AWS Security Group - Only DMZ Publicly Accessible

Severity: medium
Compliance: PCI 1.3.1, 1.1.4
Tags: AWS, PCI, Initial Access:Exploit Public-Facing Application
Reference: https://en.wikipedia.org/wiki/DMZ_(computing)
Source: github.com/panther-labs/panther-analysis

This policy validates that only Security Groups designated as DMZs allow inbound traffic from public IP space. This helps ensure no traffic is bypassing the DMZ.

MITRE ATT&CK coverage

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

Rule body yaml

AnalysisType: policy
Filename: aws_only_dmz_security_groups_publicly_accessible.py
PolicyID: "AWS.SecurityGroup.OnlyDMZPubliclyAccessible"
DisplayName: "AWS Security Group - Only DMZ Publicly Accessible"
Enabled: false
ResourceTypes:
  - AWS.EC2.SecurityGroup
Tags:
  - AWS
  - PCI
  - Initial Access:Exploit Public-Facing Application
Reports:
  PCI:
    - 1.3.1
    - 1.1.4
  MITRE ATT&CK:
    - TA0001:T1190
Severity: Medium
Description: >
  This policy validates that only Security Groups designated as DMZs allow inbound traffic from public IP space. This helps ensure no traffic is bypassing the DMZ.
Runbook: >
  Remove the IP permissions in non-DMZ Security Groups that are allowing inbound traffic from public IP space.
Reference: https://en.wikipedia.org/wiki/DMZ_(computing)
Tests:
  - Name: DMZ Security Group Does Allows Public Access
    ExpectedResult: true
    Mocks:
      - objectName: DMZ_TAGS
        returnValue: '[["environment", "dmz"]]'
    Resource:
      {
        "Description": "example VPC security group",
        "GroupId": "sg-abc123",
        "GroupName": "default",
        "IpPermissions":
          [
            {
              "FromPort": null,
              "IpProtocol": "-1",
              "IpRanges": null,
              "Ipv6Ranges": null,
              "PrefixListIds": null,
              "ToPort": null,
              "UserIdGroupPairs":
                [
                  {
                    "Description": null,
                    "GroupId": "sg-def123",
                    "GroupName": null,
                    "PeeringStatus": null,
                    "UserId": "123456789012",
                    "VpcId": null,
                    "VpcPeeringConnectionId": null,
                  },
                ],
            },
            {
              "FromPort": null,
              "IpProtocol": "-1",
              "IpRanges": [{ "CidrIp": "1.0.0.0/24", "Description": null }],
              "Ipv6Ranges": null,
              "PrefixListIds": null,
              "ToPort": null,
              "UserIdGroupPairs": null,
            },
          ],
        "IpPermissionsEgress":
          [
            {
              "FromPort": null,
              "IpProtocol": "-1",
              "IpRanges": [{ "CidrIp": "0.0.0.0/0", "Description": null }],
              "Ipv6Ranges": null,
              "PrefixListIds": null,
              "ToPort": null,
              "UserIdGroupPairs": null,
            },
          ],
        "OwnerId": "123456789012",
        "Tags": { "environment": "dmz" },
        "VpcId": "vpc-abc111222333",
      }
  - Name: Non DMZ Security Group Allows Public Access
    ExpectedResult: false
    Mocks:
      - objectName: DMZ_TAGS
        returnValue: '[["environment", "dmz"]]'
    Resource:
      {
        "Description": "example VPC security group",
        "GroupId": "sg-abc123",
        "GroupName": "default",
        "IpPermissions":
          [
            {
              "FromPort": null,
              "IpProtocol": "-1",
              "IpRanges": null,
              "Ipv6Ranges": null,
              "PrefixListIds": null,
              "ToPort": null,
              "UserIdGroupPairs":
                [
                  {
                    "Description": null,
                    "GroupId": "sg-def123",
                    "GroupName": null,
                    "PeeringStatus": null,
                    "UserId": "123456789012",
                    "VpcId": null,
                    "VpcPeeringConnectionId": null,
                  },
                ],
            },
            {
              "FromPort": null,
              "IpProtocol": "-1",
              "IpRanges": [{ "CidrIp": "1.1.1.1/32", "Description": null }],
              "Ipv6Ranges": null,
              "PrefixListIds": null,
              "ToPort": null,
              "UserIdGroupPairs": null,
            },
          ],
        "IpPermissionsEgress":
          [
            {
              "FromPort": null,
              "IpProtocol": "-1",
              "IpRanges": [{ "CidrIp": "192.0.2.0/24", "Description": null }],
              "Ipv6Ranges": null,
              "PrefixListIds": null,
              "ToPort": null,
              "UserIdGroupPairs": null,
            },
          ],
        "OwnerId": "123456789012",
        "Tags": { "environment": "pci" },
        "VpcId": "vpc-abc111222333",
      }
  - Name: Non DMZ Security Group Does Not Allow Public Access
    ExpectedResult: true
    Mocks:
      - objectName: DMZ_TAGS
        returnValue: '[["environment", "dmz"]]'
    Resource:
      {
        "Description": "example VPC security group",
        "GroupId": "sg-abc123",
        "GroupName": "default",
        "IpPermissions":
          [
            {
              "FromPort": null,
              "IpProtocol": "-1",
              "IpRanges": null,
              "Ipv6Ranges": null,
              "PrefixListIds": null,
              "ToPort": null,
              "UserIdGroupPairs":
                [
                  {
                    "Description": null,
                    "GroupId": "sg-def123",
                    "GroupName": null,
                    "PeeringStatus": null,
                    "UserId": "123456789012",
                    "VpcId": null,
                    "VpcPeeringConnectionId": null,
                  },
                ],
            },
            {
              "FromPort": null,
              "IpProtocol": "-1",
              "IpRanges": [{ "CidrIp": "192.168.0.0/24", "Description": null }],
              "Ipv6Ranges": null,
              "PrefixListIds": null,
              "ToPort": null,
              "UserIdGroupPairs": null,
            },
          ],
        "IpPermissionsEgress":
          [
            {
              "FromPort": null,
              "IpProtocol": "-1",
              "IpRanges": [{ "CidrIp": "192.0.2.0/24", "Description": null }],
              "Ipv6Ranges": null,
              "PrefixListIds": null,
              "ToPort": null,
              "UserIdGroupPairs": null,
            },
          ],
        "OwnerId": "123456789012",
        "Tags": { "environment": "pci" },
        "VpcId": "vpc-abc111222333",
      }

Detection logic

Condition

not (IpPermissions is_null or Tags is_not_null)

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
`Tags`	is_not_null	(no value, null check)
`IpPermissions`	is_null	(no value, null check)

`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)