ACFP example: Custom response for compromised credentials

By default, the credentials check that's performed by the rule group AWSManagedRulesACFPRuleSet handles compromised credentials by labeling the request and blocking it. For details about the rule group and rule behavior, see Amazon WAF Fraud Control account creation fraud prevention (ACFP) rule group.

To inform the user that the account credentials they've provided have been compromised, you can do the following:

The following web ACL listings shows the ACFP managed rule group from the prior example, with the SignalCredentialCompromised rule action overridden to count. With this configuration, when this rule group evaluates any web request that uses compromised credentials, it will label the request, but not block it.

In addition, the web ACL now has a custom response named aws-waf-credential-compromised and a new rule named AccountSignupCompromisedCredentialsHandling. The rule priority is a higher numeric setting than the rule group, so it runs after the rule group in the web ACL evaluation. The new rule matches any request with the rule group's compromised credentials label. When the rule finds a match, it applies the Block action to the request with the custom response body. The custom response body provides information to the end user that their credentials have been compromised and proposes an action to take.

{
  "Name": "compromisedCreds",
  "Id": "... ",
  "ARN": "arn:aws:wafv2:us-east-1:111122223333:regional/webacl/compromisedCreds/...",
  "DefaultAction": {
    "Allow": {}
  },
  "Description": "",
  "Rules": [
    {
      "Name": "AWS-AWSManagedRulesACFPRuleSet",
      "Priority": 0,
      "Statement": {
        "ManagedRuleGroupStatement": {
          "VendorName": "AWS",
          "Name": "AWSManagedRulesACFPRuleSet",
          "ManagedRuleGroupConfigs": [
            {
              "AWSManagedRulesACFPRuleSet": {
                "CreationPath": "/web/signup/submit-registration",
                "RegistrationPagePath": "/web/signup/registration",
                "RequestInspection": {
                  "PayloadType": "JSON",
                  "UsernameField": {
                    "Identifier": "/form/username"
                  },
                  "PasswordField": {
                    "Identifier": "/form/password"
                  },
                  "EmailField": {
                    "Identifier": "/form/email"
                  },
                  "PhoneNumberFields": [
                    {
                      "Identifier": "/form/country-code"
                    },
                    {
                      "Identifier": "/form/region-code"
                    },
                    {
                      "Identifier": "/form/phonenumber"
                    }
                  ],
                  "AddressFields": [
                    {
                      "Identifier": "/form/name"
                    },
                    {
                      "Identifier": "/form/street-address"
                    },
                    {
                      "Identifier": "/form/city"
                    },
                    {
                      "Identifier": "/form/state"
                    },
                    {
                      "Identifier": "/form/zipcode"
                    }
                  ]
                },
                "EnableRegexInPath": false
              }
            }
          ],
          "RuleActionOverrides": [
            {
              "Name": "SignalCredentialCompromised",
              "ActionToUse": {
                "Count": {}
              }
            }
          ]
        }
      },
      "OverrideAction": {
        "None": {}
      },
      "VisibilityConfig": {
        "SampledRequestsEnabled": true,
        "CloudWatchMetricsEnabled": true,
        "MetricName": "AWS-AWSManagedRulesACFPRuleSet"
      }
    },
    {
      "Name": "AccountSignupCompromisedCredentialsHandling",
      "Priority": 1,
      "Statement": {
        "LabelMatchStatement": {
          "Scope": "LABEL",
          "Key": "awswaf:managed:aws:acfp:signal:credential_compromised"
        }
      },
      "Action": {
        "Block": {
          "CustomResponse": {
            "ResponseCode": 406,
            "CustomResponseBodyKey": "aws-waf-credential-compromised",
            "ResponseHeaders": [
              {
                "Name": "aws-waf-credential-compromised",
                "Value": "true"
              }
            ]
          }
        }
      },
      "VisibilityConfig": {
        "SampledRequestsEnabled": true,
        "CloudWatchMetricsEnabled": true,
        "MetricName": "AccountSignupCompromisedCredentialsHandling"
      }
    }
  ],
  "VisibilityConfig": {
    "SampledRequestsEnabled": true,
    "CloudWatchMetricsEnabled": true,
    "MetricName": "compromisedCreds"
  },
  "Capacity": 51,
  "ManagedByFirewallManager": false,
  "LabelNamespace": "awswaf:111122223333:webacl:compromisedCreds:",
  "CustomResponseBodies": {
    "aws-waf-credential-compromised": {
      "ContentType": "APPLICATION_JSON",
      "Content": "{\n  \"credentials-compromised\": \"The credentials you provided have been found in a compromised credentials database.\\n\\nTry again with a different username, password pair.\"\n}"
    }
  }
}