Using labels on web requests in AWS WAF

Evaluating a web request against multiple rule statements before taking action on the request – After a match is found with a rule in a web ACL, AWS WAF continues evaluating the request against the web ACL if the rule action doesn't terminate the web ACL evaluation. You can use labels to evaluate and collect information from multiple rules before you decide to allow or block the request. To do this, change the actions for your existing rules to Count and configure them to add labels to matching requests. Then, add one or more new rules to run after your other rules, and configure them to evaluate the labels and manage the requests according to the label match combinations.

Managing web requests by geographical region – You can use the geographic match rule alone to manage web requests by the country of origin. To fine-tune the location down to the region level, you use the geo match rule with a Count action followed by a label match rule. For information about the geo match rule, see Geographic match rule statement.

Reusing logic across multiple rules – If you need to reuse the same logic across multiple rules, you can use labels to single-source the logic and just test for the results. When you have multiple complex rules that use a common subset of nested rule statements, duplicating the common rule set across your complex rules can be time consuming and error prone. With labels, you can create a new rule with the common rule subset that counts matching requests and adds a label to them. You add the new rule to your web ACL so that it runs before your original complex rules. Then, in your original rules, you replace the shared rule subset with a single rule that checks for the label.

For example, say you have multiple rules that you want to only apply to your login paths. Rather than have each rule specify the same logic to match potential login paths, you can implement a single new rule that contains that logic. Have the new rule add a label to matching requests to indicate that the request is on a login path. In your web ACL, give this new rule a lower numeric priority setting than your original rules so that it runs first. Then, in your original rules, replace the shared logic with a check for the presence of the label. For information about priority settings, see Setting rule priority in a web ACL.

Creating exceptions to rules in rule groups – This option is particularly useful for managed rule groups, which you can't view or alter. Many managed rule group rules add labels to matching web requests, to indicate the rules that matched and possibly to provide additional information about the match. When you use a rule group that adds labels to requests, you can override the rule group rules to count matches, and then run a rule after the rule group that handles the web request based on the rule group labels. All AWS Managed Rules add labels to matching web requests. For details, see the rule descriptions at AWS Managed Rules rule groups list.

Using label metrics to monitor traffic patterns – You can access metrics for labels that you add through your rules and for metrics added by any managed rule groups that you use in your web ACL. All of the AWS Managed Rules rule groups add labels to the web requests that they evaluate. For a list of label metrics and dimensions, see Label metrics and dimensions. You can access metrics and metric summaries through CloudWatch and through the web ACL page in the AWS WAF console. For information, see Monitoring and tuning your AWS WAF protections.