8-3 WAF Rule Sets

Key Concepts

• Core Rule Set (CRS)
• OWASP ModSecurity Core Rule Set
• Custom Rule Sets
• Rate Limiting Rules
• Geolocation-Based Rules
• IP Blacklisting and Whitelisting
• Behavioral Analysis Rules
• Protocol Compliance Rules

Core Rule Set (CRS)

The Core Rule Set (CRS) is a collection of generic attack detection rules for use with ModSecurity or compatible web application firewalls. It is designed to protect web applications from a wide range of attacks, including SQL injection, XSS, and other common vulnerabilities.

Example: The CRS includes rules to detect and block SQL injection attempts by looking for specific patterns in the request payload.

OWASP ModSecurity Core Rule Set

The OWASP ModSecurity Core Rule Set is a community-maintained version of the Core Rule Set, developed by the Open Web Application Security Project (OWASP). It provides a comprehensive set of rules to protect against a variety of web application attacks.

Example: The OWASP CRS includes rules to detect and block cross-site scripting (XSS) attacks by examining the content of HTTP requests for malicious scripts.

Custom Rule Sets

Custom Rule Sets are tailored rules created to address specific security concerns or vulnerabilities unique to a particular web application. These rules can be based on the Core Rule Set but are modified to fit the application's specific needs.

Example: A custom rule set might be created to block specific types of file uploads that are known to be exploited in the application's environment.

Rate Limiting Rules

Rate Limiting Rules are used to control the number of requests a client can make to a web application within a certain time period. This helps prevent denial-of-service (DoS) attacks and other forms of abuse.

Example: A rate limiting rule might limit the number of login attempts a user can make in a minute to prevent brute-force attacks.

Geolocation-Based Rules

Geolocation-Based Rules use the geographic location of the client to enforce security policies. These rules can block or allow requests based on the client's country or region.

Example: A geolocation-based rule might block all requests from countries known for high levels of cybercrime.

IP Blacklisting and Whitelisting

IP Blacklisting and Whitelisting involve creating lists of IP addresses that are either allowed or denied access to the web application. Blacklisting blocks known malicious IPs, while whitelisting allows only trusted IPs.

Example: An IP blacklist might include addresses associated with known attackers, while a whitelist might include only internal company IPs.

Behavioral Analysis Rules

Behavioral Analysis Rules monitor the behavior of users and detect anomalies that may indicate malicious activity. These rules can identify patterns of behavior that are indicative of attacks, such as unusual login times or atypical navigation paths.

Example: A behavioral analysis rule might detect a user logging in from multiple locations within a short period, flagging it as a potential account takeover attempt.

Protocol Compliance Rules

Protocol Compliance Rules ensure that HTTP requests adhere to the standards defined by the HTTP protocol. These rules help prevent attacks that exploit deviations from the protocol, such as HTTP request smuggling or header injection.

Example: A protocol compliance rule might reject requests with malformed headers to prevent header injection attacks.

Examples and Analogies

Think of the Core Rule Set as a standard security manual for a building, the OWASP CRS as a community-updated version, custom rule sets as site-specific security protocols, rate limiting rules as visitor limits, geolocation-based rules as country-specific access policies, IP blacklisting and whitelisting as guest lists, behavioral analysis rules as security guards monitoring activity, and protocol compliance rules as enforcing the building's fire code.

Insightful Value

Understanding WAF Rule Sets is crucial for configuring a Web Application Firewall (WAF) to protect your web applications effectively. By leveraging Core Rule Sets, customizing them to fit your application's needs, and implementing additional rules like rate limiting, geolocation-based controls, IP blacklisting and whitelisting, behavioral analysis, and protocol compliance, you can create a multi-layered defense against a wide range of web application threats.