AWS Application Load Balancer Web ACL

Severity: high
Tags: AWS, Configuration Required, Security Control, Initial Access:Exploit Public-Facing Application
Reference: https://aws.amazon.com/blogs/aws/aws-web-application-firewall-waf-for-application-load-balancers/
Source: github.com/panther-labs/panther-analysis

This policy validates that all application load balancers have an associated Web ACl to enforce protections against various web attacks.

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1190` Exploit Public-Facing Application

Rule body yaml

AnalysisType: policy
Filename: aws_application_load_balancer_web_acl.py
PolicyID: "AWS.ApplicationLoadBalancer.WebACL"
DisplayName: "AWS Application Load Balancer Web ACL"
Enabled: false
ResourceTypes:
  - AWS.ELBV2.ApplicationLoadBalancer
Tags:
  - AWS
  - Configuration Required
  - Security Control
  - Initial Access:Exploit Public-Facing Application
Reports:
  MITRE ATT&CK:
    - TA0001:T1190
Severity: High
Description: >
  This policy validates that all application load balancers have an associated Web ACl to enforce protections against various web attacks.
Runbook: >
  https://docs.runpanther.io/alert-runbooks/built-in-policies/aws-application-load-balancer-has-web-acl
Reference: https://aws.amazon.com/blogs/aws/aws-web-application-firewall-waf-for-application-load-balancers/
Tests:
  - Name: Load Balancer Does Not Have Required WAF Web ACL
    ExpectedResult: false
    Resource:
      {
        "AvailabilityZones":
          [
            {
              "LoadBalancerAddresses": null,
              "SubnetId": "subnet-111222333",
              "ZoneName": "us-west-2d",
            },
            {
              "LoadBalancerAddresses": null,
              "SubnetId": "subnet-111222333",
              "ZoneName": "us-west-2a",
            },
          ],
        "CanonicalHostedZoneId": "111222333AAA",
        "CreatedTime": "2019-01-01T00:00:00.00Z",
        "DNSName": "example-lb-111222333.us-west-2.elb.amazonaws.com",
        "IpAddressType": "ipv4",
        "LoadBalancerArn": "TEST_LOAD_BALANCER_ARN",
        "LoadBalancerName": "TEST_LOAD_BALANCER",
        "Scheme": "internal",
        "SecurityGroups": ["sg-111222333444"],
        "State": { "Code": "active", "Reason": null },
        "Type": "application",
        "VpcId": "vpc-111222333",
        "WebAcl": null,
      }
  - Name: Load Balancer Does Not Require WAF Web ACL
    ExpectedResult: true
    Resource:
      {
        "AvailabilityZones":
          [
            {
              "LoadBalancerAddresses": null,
              "SubnetId": "subnet-111222333",
              "ZoneName": "us-west-2d",
            },
            {
              "LoadBalancerAddresses": null,
              "SubnetId": "subnet-111222333",
              "ZoneName": "us-west-2a",
            },
          ],
        "CanonicalHostedZoneId": "111222333AAA",
        "CreatedTime": "2019-01-01T00:00:00.00Z",
        "DNSName": "example-lb-111222333.us-west-2.elb.amazonaws.com",
        "IpAddressType": "ipv4",
        "LoadBalancerArn": "TEST_LOAD_BALANCER_ARN_NO_WEB_ACL",
        "LoadBalancerName": "TEST_LOAD_BALANCER",
        "Scheme": "internal",
        "SecurityGroups": ["sg-111222333444"],
        "State": { "Code": "active", "Reason": null },
        "Type": "application",
        "VpcId": "vpc-111222333",
        "WebAcl": null,
      }
  - Name: Load Balancer Has Correct WAF Web ACL
    ExpectedResult: true
    Resource:
      {
        "AvailabilityZones":
          [
            {
              "LoadBalancerAddresses": null,
              "SubnetId": "subnet-111222333",
              "ZoneName": "us-west-2d",
            },
            {
              "LoadBalancerAddresses": null,
              "SubnetId": "subnet-111222333",
              "ZoneName": "us-west-2a",
            },
          ],
        "CanonicalHostedZoneId": "111222333AAA",
        "CreatedTime": "2019-01-01T00:00:00.00Z",
        "DNSName": "example-lb-111222333.us-west-2.elb.amazonaws.com",
        "IpAddressType": "ipv4",
        "LoadBalancerArn": "TEST_LOAD_BALANCER_ARN",
        "LoadBalancerName": "TEST_LOAD_BALANCER",
        "Scheme": "internal",
        "SecurityGroups": ["sg-111222333444"],
        "State": { "Code": "active", "Reason": null },
        "Type": "application",
        "VpcId": "vpc-111222333",
        "WebAcl":
          {
            "DefaultAction": { "Type": "ALLOW" },
            "MetricName": "examplewebacl",
            "Name": "example-web-acl",
            "Rules":
              [
                {
                  "Action": { "Type": "BLOCK" },
                  "ExcludedRules": null,
                  "OverrideAction": null,
                  "Priority": 2,
                  "RuleId": "111222-1111-1111-1111-111222333444",
                  "Type": "REGULAR",
                },
                {
                  "Action": { "Type": "COUNT" },
                  "ExcludedRules": null,
                  "OverrideAction": null,
                  "Priority": 1,
                  "RuleId": "111222-1111-2222-3333-111222333444",
                  "Type": "REGULAR",
                },
              ],
            "WebACLArn": "arn:aws:waf-regional:us-west-2:123456789012:webacl/111222-1111-2222-3333-111222333444",
            "WebACLId": "TEST_WAF_WEB_ACL_ID",
          },
      }

Detection logic

Condition

not (WebAcl is_not_null and LoadBalancerArn not in "TEST_LOAD_BALANCER_ARN")

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
`LoadBalancerArn`	eq	`TEST_LOAD_BALANCER_ARN`
`WebAcl`	is_not_null	(no value, null check)

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
`LoadBalancerArn`	in	`TEST_LOAD_BALANCER_ARN`

`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)