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Web Application Firewall DRS rule groups and rules

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Azure Front Door web application firewall (WAF) protects web applications from common vulnerabilities and exploits. Azure-managed rule sets provide an easy way to deploy protection against a common set of security threats. Since such rule sets are managed by Azure, the rules are updated as needed to protect against new attack signatures. Default rule set also includes the Microsoft Threat Intelligence Collection rules that are written in partnership with the Microsoft Intelligence team to provide increased coverage, patches for specific vulnerabilities, and better false positive reduction.

Default rule sets

Azure-managed Default Rule Set includes rules against the following threat categories:

  • Cross-site scripting
  • Java attacks
  • Local file inclusion
  • PHP injection attacks
  • Remote command execution
  • Remote file inclusion
  • Session fixation
  • SQL injection protection
  • Protocol attackers

The version number of the Default Rule Set increments when new attack signatures are added to the rule set. Default Rule Set is enabled by default in Detection mode in your WAF policies. You can disable or enable individual rules within the Default Rule Set to meet your application requirements. You can also set specific actions (ALLOW/BLOCK/REDIRECT/LOG) per rule.

Sometimes you may need to omit certain request attributes from a WAF evaluation. A common example is Active Directory-inserted tokens that are used for authentication. You may configure an exclusion list for a managed rule, rule group, or for the entire rule set.

The Default action is to BLOCK. Additionally, custom rules can be configured in the same WAF policy if you wish to bypass any of the pre-configured rules in the Default Rule Set.

Custom rules are always applied before rules in the Default Rule Set are evaluated. If a request matches a custom rule, the corresponding rule action is applied. The request is either blocked or passed through to the back-end. No other custom rules or the rules in the Default Rule Set are processed. You can also remove the Default Rule Set from your WAF policies.

Microsoft Threat Intelligence Collection rules

The Microsoft Threat Intelligence Collection rules are written in partnership with the Microsoft Intelligence team to provide increased coverage, patches for specific vulnerabilities, and better false positive reduction.

Anomaly Scoring mode

OWASP has two modes for deciding whether to block traffic: Traditional mode and Anomaly Scoring mode.

In Traditional mode, traffic that matches any rule is considered independently of any other rule matches. This mode is easy to understand. But the lack of information about how many rules match a specific request is a limitation. So, Anomaly Scoring mode was introduced. It's the default for OWASP 3.x.

In Anomaly Scoring mode, traffic that matches any rule isn't immediately blocked when the firewall is in Prevention mode. Rules have a certain severity: Critical, Error, Warning, or Notice. That severity affects a numeric value for the request, which is called the Anomaly Score. For example, one Warning rule match contributes 3 to the score. One Critical rule match contributes 5.

Severity Value
Critical 5
Error 4
Warning 3
Notice 2

There's a threshold of 5 for the Anomaly Score to block traffic. So, a single Critical rule match is enough for the WAF to block a request, even in Prevention mode. But one Warning rule match only increases the Anomaly Score by 3, which isn't enough by itself to block the traffic. For more information, see What content types does WAF support? in the FAQ to learn what content types are supported for body inspection with different DRS versions.

DRS 2.0

DRS 2.0 includes 17 rule groups, as shown in the following table. Each group contains multiple rules, which can be disabled.

Note

DRS 2.0 is only available on Azure Front Door Premium.

Rule group Description
General General group
METHOD-ENFORCEMENT Lock-down methods (PUT, PATCH)
PROTOCOL-ENFORCEMENT Protect against protocol and encoding issues
PROTOCOL-ATTACK Protect against header injection, request smuggling, and response splitting
APPLICATION-ATTACK-LFI Protect against file and path attacks
APPLICATION-ATTACK-RFI Protect against remote file inclusion (RFI) attacks
APPLICATION-ATTACK-RCE Protect again remote code execution attacks
APPLICATION-ATTACK-PHP Protect against PHP-injection attacks
APPLICATION-ATTACK-NodeJS Protect against Node JS attacks
APPLICATION-ATTACK-XSS Protect against cross-site scripting attacks
APPLICATION-ATTACK-SQLI Protect against SQL-injection attacks
APPLICATION-ATTACK-SESSION-FIXATION Protect against session-fixation attacks
APPLICATION-ATTACK-SESSION-JAVA Protect against JAVA attacks
MS-ThreatIntel-WebShells Protect against Web shell attacks
MS-ThreatIntel-AppSec Protect against AppSec attacks
MS-ThreatIntel-SQLI Protect against SQLI attacks
MS-ThreatIntel-CVEs Protect against CVE attacks

DRS 1.1

Rule group Description
PROTOCOL-ATTACK Protect against header injection, request smuggling, and response splitting
APPLICATION-ATTACK-LFI Protect against file and path attacks
APPLICATION-ATTACK-RFI Protection against remote file inclusion attacks
APPLICATION-ATTACK-RCE Protection against remote command execution
APPLICATION-ATTACK-PHP Protect against PHP-injection attacks
APPLICATION-ATTACK-XSS Protect against cross-site scripting attacks
APPLICATION-ATTACK-SQLI Protect against SQL-injection attacks
APPLICATION-ATTACK-SESSION-FIXATION Protect against session-fixation attacks
APPLICATION-ATTACK-SESSION-JAVA Protect against JAVA attacks
MS-ThreatIntel-WebShells Protect against Web shell attacks
MS-ThreatIntel-AppSec Protect against AppSec attacks
MS-ThreatIntel-SQLI Protect against SQLI attacks
MS-ThreatIntel-CVEs Protect against CVE attacks

DRS 1.0

Rule group Description
PROTOCOL-ATTACK Protect against header injection, request smuggling, and response splitting
APPLICATION-ATTACK-LFI Protect against file and path attacks
APPLICATION-ATTACK-RFI Protection against remote file inclusion attacks
APPLICATION-ATTACK-RCE Protection against remote command execution
APPLICATION-ATTACK-PHP Protect against PHP-injection attacks
APPLICATION-ATTACK-XSS Protect against cross-site scripting attacks
APPLICATION-ATTACK-SQLI Protect against SQL-injection attacks
APPLICATION-ATTACK-SESSION-FIXATION Protect against session-fixation attacks
APPLICATION-ATTACK-SESSION-JAVA Protect against JAVA attacks
MS-ThreatIntel-WebShells Protect against Web shell attacks
MS-ThreatIntel-CVEs Protect against CVE attacks

Bot rules

Rule group Description
BadBots Protect against bad bots
GoodBots Identify good bots
UnknownBots Identify unknown bots

The following rule groups and rules are available when using Web Application Firewall on Azure Front Door.

2.0 rule sets

General

RuleId Description
200002 Failed to parse request body.
200003 Multipart request body failed strict validation

METHOD ENFORCEMENT

RuleId Description
911100 Method is not allowed by policy

PROTOCOL-ENFORCEMENT

RuleId Description
920100 Invalid HTTP Request Line
920120 Attempted multipart/form-data bypass
920121 Attempted multipart/form-data bypass
920160 Content-Length HTTP header is not numeric.
920170 GET or HEAD Request with Body Content.
920171 GET or HEAD Request with Transfer-Encoding.
920180 POST request missing Content-Length Header.
920190 Range: Invalid Last Byte Value.
920200 Range: Too many fields (6 or more)
920201 Range: Too many fields for pdf request (35 or more)
920210 Multiple/Conflicting Connection Header Data Found.
920220 URL Encoding Abuse Attack Attempt
920230 Multiple URL Encoding Detected
920240 URL Encoding Abuse Attack Attempt
920260 Unicode Full/Half Width Abuse Attack Attempt
920270 Invalid character in request (null character)
920271 Invalid character in request (non printable characters)
920280 Request Missing a Host Header
920290 Empty Host Header
920300 Request Missing an Accept Header
920310 Request Has an Empty Accept Header
920311 Request Has an Empty Accept Header
920320 Missing User Agent Header
920330 Empty User Agent Header
920340 Request Containing Content, but Missing Content-Type header
920341 Request containing content requires Content-Type header
920350 Host header is a numeric IP address
920420 Request content type is not allowed by policy
920430 HTTP protocol version is not allowed by policy
920440 URL file extension is restricted by policy
920450 HTTP header is restricted by policy
920470 Illegal Content-Type header
920480 Request content type charset is not allowed by policy

PROTOCOL-ATTACK

RuleId Description
921110 HTTP Request Smuggling Attack
921120 HTTP Response Splitting Attack
921130 HTTP Response Splitting Attack
921140 HTTP Header Injection Attack via headers
921150 HTTP Header Injection Attack via payload (CR/LF detected)
921151 HTTP Header Injection Attack via payload (CR/LF detected)
921160 HTTP Header Injection Attack via payload (CR/LF and header-name detected)

LFI - Local File Inclusion

RuleId Description
930100 Path Traversal Attack (/../)
930110 Path Traversal Attack (/../)
930120 OS File Access Attempt
930130 Restricted File Access Attempt

RFI - Remote File Inclusion

RuleId Description
931100 Possible Remote File Inclusion (RFI) Attack: URL Parameter using IP Address
931110 Possible Remote File Inclusion (RFI) Attack: Common RFI Vulnerable Parameter Name used w/URL Payload
931120 Possible Remote File Inclusion (RFI) Attack: URL Payload Used w/Trailing Question Mark Character (?)
931130 Possible Remote File Inclusion (RFI) Attack: Off-Domain Reference/Link

RCE - Remote Command Execution

RuleId Description
932100 Remote Command Execution: Unix Command Injection
932105 Remote Command Execution: Unix Command Injection
932110 Remote Command Execution: Windows Command Injection
932115 Remote Command Execution: Windows Command Injection
932120 Remote Command Execution: Windows PowerShell Command Found
932130 Remote Command Execution: Unix Shell Expression or Confluence Vulnerability (CVE-2022-26134) Found
932140 Remote Command Execution: Windows FOR/IF Command Found
932150 Remote Command Execution: Direct Unix Command Execution
932160 Remote Command Execution: Unix Shell Code Found
932170 Remote Command Execution: Shellshock (CVE-2014-6271)
932171 Remote Command Execution: Shellshock (CVE-2014-6271)
932180 Restricted File Upload Attempt

PHP Attacks

RuleId Description
933100 PHP Injection Attack: Opening/Closing Tag Found
933110 PHP Injection Attack: PHP Script File Upload Found
933120 PHP Injection Attack: Configuration Directive Found
933130 PHP Injection Attack: Variables Found
933140 PHP Injection Attack: I/O Stream Found
933150 PHP Injection Attack: High-Risk PHP Function Name Found
933151 PHP Injection Attack: Medium-Risk PHP Function Name Found
933160 PHP Injection Attack: High-Risk PHP Function Call Found
933170 PHP Injection Attack: Serialized Object Injection
933180 PHP Injection Attack: Variable Function Call Found
933200 PHP Injection Attack: Wrapper scheme detected
933210 PHP Injection Attack: Variable Function Call Found

Node JS Attacks

RuleId Description
934100 Node.js Injection Attack

XSS - Cross-site Scripting

RuleId Description
941100 XSS Attack Detected via libinjection
941101 XSS Attack Detected via libinjection.
941110 XSS Filter - Category 1: Script Tag Vector
941120 XSS Filter - Category 2: Event Handler Vector
941130 XSS Filter - Category 3: Attribute Vector
941140 XSS Filter - Category 4: JavaScript URI Vector
941150 XSS Filter - Category 5: Disallowed HTML Attributes
941160 NoScript XSS InjectionChecker: HTML Injection
941170 NoScript XSS InjectionChecker: Attribute Injection
941180 Node-Validator Blacklist Keywords
941190 XSS Using style sheets
941200 XSS using VML frames
941210 XSS using obfuscated JavaScript
941220 XSS using obfuscated VB Script
941230 XSS using 'embed' tag
941240 XSS using 'import' or 'implementation' attribute
941250 IE XSS Filters - Attack Detected.
941260 XSS using 'meta' tag
941270 XSS using 'link' href
941280 XSS using 'base' tag
941290 XSS using 'applet' tag
941300 XSS using 'object' tag
941310 US-ASCII Malformed Encoding XSS Filter - Attack Detected.
941320 Possible XSS Attack Detected - HTML Tag Handler
941330 IE XSS Filters - Attack Detected.
941340 IE XSS Filters - Attack Detected.
941350 UTF-7 Encoding IE XSS - Attack Detected.
941360 JavaScript obfuscation detected.
941370 JavaScript global variable found
941380 AngularJS client side template injection detected

Note

This article contains references to the term blacklist, a term that Microsoft no longer uses. When the term is removed from the software, we’ll remove it from this article.

SQLI - SQL Injection

RuleId Description
942100 SQL Injection Attack Detected via libinjection
942110 SQL Injection Attack: Common Injection Testing Detected
942120 SQL Injection Attack: SQL Operator Detected
942130 SQL Injection Attack: SQL Tautology Detected.
942140 SQL Injection Attack: Common DB Names Detected
942150 SQL Injection Attack
942160 Detects blind sqli tests using sleep() or benchmark().
942170 Detects SQL benchmark and sleep injection attempts including conditional queries
942180 Detects basic SQL authentication bypass attempts 1/3
942190 Detects MSSQL code execution and information gathering attempts
942200 Detects MySQL comment-/space-obfuscated injections and backtick termination
942210 Detects chained SQL injection attempts 1/2
942220 Looking for integer overflow attacks, these are taken from skipfish, except 3.0.00738585072007e-308 is the "magic number" crash
942230 Detects conditional SQL injection attempts
942240 Detects MySQL charset switch and MSSQL DoS attempts
942250 Detects MATCH AGAINST, MERGE and EXECUTE IMMEDIATE injections
942260 Detects basic SQL authentication bypass attempts 2/3
942270 Looking for basic sql injection. Common attack string for mysql, oracle, and others.
942280 Detects Postgres pg_sleep injection, waitfor delay attacks and database shutdown attempts
942290 Finds basic MongoDB SQL injection attempts
942300 Detects MySQL comments, conditions, and ch(a)r injections
942310 Detects chained SQL injection attempts 2/2
942320 Detects MySQL and PostgreSQL stored procedure/function injections
942330 Detects classic SQL injection probings 1/2
942340 Detects basic SQL authentication bypass attempts 3/3
942350 Detects MySQL UDF injection and other data/structure manipulation attempts
942360 Detects concatenated basic SQL injection and SQLLFI attempts
942361 Detects basic SQL injection based on keyword alter or union
942370 Detects classic SQL injection probings 2/2
942380 SQL Injection Attack
942390 SQL Injection Attack
942400 SQL Injection Attack
942410 SQL Injection Attack
942430 Restricted SQL Character Anomaly Detection (args): # of special characters exceeded (12)
942440 SQL Comment Sequence Detected.
942450 SQL Hex Encoding Identified
942460 Meta-Character Anomaly Detection Alert - Repetitive Non-Word Characters
942470 SQL Injection Attack
942480 SQL Injection Attack
942500 MySQL in-line comment detected.
942510 SQLi bypass attempt by ticks or backticks detected.

SESSION-FIXATION

RuleId Description
943100 Possible Session Fixation Attack: Setting Cookie Values in HTML
943110 Possible Session Fixation Attack: SessionID Parameter Name with Off-Domain Referrer
943120 Possible Session Fixation Attack: SessionID Parameter Name with No Referrer

JAVA Attacks

RuleId Description
944100 Remote Command Execution: Apache Struts, Oracle WebLogic
944110 Detects potential payload execution
944120 Possible payload execution and remote command execution
944130 Suspicious Java classes
944200 Exploitation of Java deserialization Apache Commons
944210 Possible use of Java serialization
944240 Remote Command Execution: Java serialization and Log4j vulnerability (CVE-2021-44228, CVE-2021-45046)
944250 Remote Command Execution: Suspicious Java method detected

MS-ThreatIntel-WebShells

RuleId Description
99005002 Web Shell Interaction Attempt (POST)
99005003 Web Shell Upload Attempt (POST) - CHOPPER PHP
99005004 Web Shell Upload Attempt (POST) - CHOPPER ASPX
99005006 Spring4Shell Interaction Attempt

MS-ThreatIntel-AppSec

RuleId Description
99030001 Path Traversal Evasion in Headers (/.././../)
99030002 Path Traversal Evasion in Request Body (/.././../)

MS-ThreatIntel-SQLI

RuleId Description
99031001 SQL Injection Attack: Common Injection Testing Detected
99031002 SQL Comment Sequence Detected.

MS-ThreatIntel-CVEs

RuleId Description
99001001 Attempted F5 tmui (CVE-2020-5902) REST API Exploitation with known credentials
99001014 Attempted Spring Cloud routing-expression injection CVE-2022-22963
99001015 Attempted Spring Framework unsafe class object exploitation CVE-2022-22965
99001016 Attempted Spring Cloud Gateway Actuator injection CVE-2022-22947

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