Deciding on the default action for a Web ACL

Note

This is AWS WAF Classic documentation. You should only use this version if you created AWS WAF resources, like rules and web ACLs, in AWS WAF prior to November 2019, and you have not migrated them over to the latest version yet. To migrate your resources, see Migrating your AWS WAF Classic resources to AWS WAF.

For the latest version of AWS WAF, see AWS WAF.

When you create and configure a web ACL, the first and most important decision that you must make is whether the default action should be for AWS WAF Classic to allow web requests or to block web requests. The default action indicates what you want AWS WAF Classic to do after it inspects a web request for all the conditions that you specify, and the web request doesn't match any of those conditions:

• Allow – If you want to allow most users to access your website, but you want to block access to attackers whose requests originate from specified IP addresses, or whose requests appear to contain malicious SQL code or specified values, choose Allow for the default action.

• Block – If you want to prevent most would-be users from accessing your website, but you want to allow access to users whose requests originate from specified IP addresses, or whose requests contain specified values, choose Block for the default action.

Many decisions that you make after you've decided on a default action depend on whether you want to allow or block most web requests. For example, if you want to allow most requests, then the match conditions that you create generally should specify the web requests that you want to block, such as the following:

• Requests that originate from IP addresses that are making an unreasonable number of requests

• Requests that originate from countries that either you don't do business in or are the frequent source of attacks

• Requests that include fake values in the User-Agent header

• Requests that appear to include malicious SQL code