AWS WAF Rule Ordering

Severity: high
Tags: AWS, Configuration Required, Security Control
Reference: https://docs.aws.amazon.com/waf/latest/developerguide/web-acl-rules.html
Source: github.com/panther-labs/panther-analysis

This policy validates that all WAF's have the correct rule ordering. Incorrect rule ordering could lead to less restrictive rules being matched and allowing traffic through before more restrictive rules that should have blocked the traffic.

Rule body yaml

AnalysisType: policy
Filename: aws_waf_rule_ordering.py
PolicyID: "AWS.WAF.RuleOrdering"
DisplayName: "AWS WAF Rule Ordering"
Enabled: false
ResourceTypes:
  - AWS.WAF.Regional.WebACL
  - AWS.WAF.WebACL
Tags:
  - AWS
  - Configuration Required
  - Security Control
Severity: High
Description: >
  This policy validates that all WAF's have the correct rule ordering. Incorrect rule ordering could lead to less restrictive rules being matched and allowing traffic through before more restrictive rules that should have blocked the traffic.
Runbook: >
  https://docs.runpanther.io/alert-runbooks/built-in-policies/aws-waf-has-correct-rule-ordering
Reference: https://docs.aws.amazon.com/waf/latest/developerguide/web-acl-rules.html
Tests:
  - Name: Web ACL Configured Properly
    ExpectedResult: true
    Resource:
      {
        "DefaultAction": { "Type": "ALLOW" },
        "MetricName": "examplewebacl",
        "Name": "example-web-acl",
        "Rules":
          [
            {
              "Action": { "Type": "BLOCK" },
              "ExcludedRules": null,
              "OverrideAction": null,
              "Priority": 2,
              "RuleId": "EXAMPLE_RULE_2_ID",
              "Type": "REGULAR",
            },
            {
              "Action": { "Type": "COUNT" },
              "ExcludedRules": null,
              "OverrideAction": null,
              "Priority": 1,
              "RuleId": "EXAMPLE_RULE_1_ID",
              "Type": "REGULAR",
            },
          ],
        "WebACLArn": "arn:aws:waf-regional:us-west-2:123456789012:webacl/11112222-3333-4444",
        "WebACLId": "EXAMPLE_WEB_ACL_ID",
      }
  - Name: Web ACL Has Incorrect Rules
    ExpectedResult: false
    Resource:
      {
        "DefaultAction": { "Type": "ALLOW" },
        "MetricName": "examplewebacl",
        "Name": "example-web-acl",
        "Rules":
          [
            {
              "Action": { "Type": "BLOCK" },
              "ExcludedRules": null,
              "OverrideAction": null,
              "Priority": 2,
              "RuleId": "111222-1111-2222-3333-111222333444",
              "Type": "REGULAR",
            },
            {
              "Action": { "Type": "COUNT" },
              "ExcludedRules": null,
              "OverrideAction": null,
              "Priority": 1,
              "RuleId": "111222-1111-1111-2222-111222333444",
              "Type": "REGULAR",
            },
          ],
        "WebACLArn": "arn:aws:waf-regional:us-west-2:123456789012:webacl/11112222-3333-4444",
        "WebACLId": "EXAMPLE_WEB_ACL_ID",
      }
  - Name: Web ACL Has Rules In Incorrect Order
    ExpectedResult: false
    Resource:
      {
        "DefaultAction": { "Type": "ALLOW" },
        "MetricName": "examplewebacl",
        "Name": "example-web-acl",
        "Rules":
          [
            {
              "Action": { "Type": "BLOCK" },
              "ExcludedRules": null,
              "OverrideAction": null,
              "Priority": 2,
              "RuleId": "EXAMPLE_RULE_1_ID",
              "Type": "REGULAR",
            },
            {
              "Action": { "Type": "COUNT" },
              "ExcludedRules": null,
              "OverrideAction": null,
              "Priority": 1,
              "RuleId": "EXAMPLE_RULE_2_ID",
              "Type": "REGULAR",
            },
          ],
        "WebACLArn": "arn:aws:waf-regional:us-west-2:123456789012:webacl/11112222-3333-4444",
        "WebACLId": "EXAMPLE_WEB_ACL_ID",
      }
  - Name: Web ACL Has No Ordering Configured
    ExpectedResult: true
    Resource:
      {
        "DefaultAction": { "Type": "ALLOW" },
        "MetricName": "examplewebacl",
        "Name": "example-web-acl",
        "Rules":
          [
            {
              "Action": { "Type": "BLOCK" },
              "ExcludedRules": null,
              "OverrideAction": null,
              "Priority": 2,
              "RuleId": "111222-1111-2222-3333-111222333444",
              "Type": "REGULAR",
            },
            {
              "Action": { "Type": "COUNT" },
              "ExcludedRules": null,
              "OverrideAction": null,
              "Priority": 1,
              "RuleId": "111222-1111-1111-2222-111222333444",
              "Type": "REGULAR",
            },
          ],
        "WebACLArn": "arn:aws:waf-regional:us-west-2:123456789012:webacl/11112222-3333-4444",
        "WebACLId": "11112222-3333-4444",
      }

Detection logic

Condition

 not not

This rule also runs imperative logic the parser cannot express as a filter; the conditions above are the structured part it could extract.

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

Field	Kind	Excluded values
`WebACLId`	eq	`EXAMPLE_WEB_ACL_ID`

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`WebACLId`	in	`EXAMPLE_WEB_ACL_ID`

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)