Creating a Regex Pattern Set in AWS WAF

AWS Web Application Firewall (WAF) is a powerful tool for protecting your web applications from various types of attacks. A Regex Pattern Set in AWS WAF enables you to match complex string patterns, helping to filter malicious requests or enforce specific rules. Here’s a step-by-step guide on creating a Regex Pattern Set in AWS WAF.

Understand Your Use Case

• Log in to your AWS Management Console.
• Navigate to WAF & Shield from the Services menu.

• Choose Regex Pattern Sets:
  • In the AWS WAF console, click on Regex Pattern Sets under the navigation pane.
• Create New Set:
  • Click on Create Regex Pattern Set.
  • Provide a meaningful name (e.g., BlockSQLPatterns) and an optional description.

• Define the regex patterns you want to match. For example:
  • .*(UNION SELECT).* (detects potential SQL injection patterns).
  • ^.*\.exe$ (matches strings ending with .exe).
  • ^[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,}$ (matches email addresses).

• Add each regex pattern one at a time, ensuring accuracy and proper testing.

• Review the added patterns.
• Click Create Regex Pattern Set to save.

Associate the Regex Pattern Set with a Rule

Create or Edit a Rule:

• • Go to the Web ACLs section and select the Web ACL where you want to apply the Regex Pattern Set.
  • Add a new rule or edit an existing one.

Define a Match Condition:

• • In the rule editor, choose the Regex Pattern Set match condition.
  • Select your newly created Regex Pattern Set.
  • Specify which part of the request to inspect (e.g., URI, headers, body).

Set the Action:

• • Configure the rule to allow, block, or count matching requests.

Save and Deploy:

• • Save the rule and deploy the updated Web ACL.

Test the Regex Pattern Set

• Use test requests to ensure the patterns match as expected.
• Adjust patterns if false positives or negatives occur.

Best Practices

• Keep Patterns Simple: Complex regex patterns can be computationally expensive.
• Test Thoroughly: Validate patterns against sample inputs to avoid unintended matches.
• Update Regularly: As threats evolve, regularly update your Regex Pattern Set to stay protected.