AWS Security Group Restricts Traffic Leaving CDE

Severity: medium
Tags: AWS, PCI, Exfiltration:Exfiltration Over Web Service
Reference: https://docs.aws.amazon.com/cli/latest/userguide/cli-services-ec2-sg.html
Source: github.com/panther-labs/panther-analysis

This policy validates that there are restrictions on what type of traffic may leave Security Groups that are considered with the scope of the PCI CDE. These restrictions help ensure that cardholder data does not leave the CDE.

MITRE ATT&CK coverage

Tactic	Techniques
Exfiltration	`T1567` Exfiltration Over Web Service

Rule body yaml

AnalysisType: policy
Filename: aws_security_group_restricts_traffic_leaving_cde.py
PolicyID: "AWS.SecurityGroup.RestrictsTrafficLeavingCDE"
DisplayName: "AWS Security Group Restricts Traffic Leaving CDE"
Enabled: false
ResourceTypes:
  - AWS.EC2.SecurityGroup
Tags:
  - AWS
  - PCI
  - Exfiltration:Exfiltration Over Web Service
Reports:
  MITRE ATT&CK:
    - TA0010:T1567
Severity: Medium
Description: >
  This policy validates that there are restrictions on what type of traffic may leave Security Groups that are considered with the scope of the PCI CDE. These restrictions help ensure that cardholder data does not leave the CDE.
Runbook: >
  Add appropriate restrictions to traffic leaving Security Groups considered a part of the CDE.
Reference: https://docs.aws.amazon.com/cli/latest/userguide/cli-services-ec2-sg.html
Tests:
  - Name: Security Group Restricts Traffic Leaving CDE
    ExpectedResult: true
    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,
                  },
                ],
            },
          ],
        "IpPermissionsEgress":
          [
            {
              "FromPort": 22,
              "IpProtocol": "-1",
              "IpRanges": [{ "CidrIp": "10.0.10.0/24", "Description": null }],
              "Ipv6Ranges": null,
              "PrefixListIds": null,
              "ToPort": 22,
              "UserIdGroupPairs": null,
            },
          ],
        "OwnerId": "123456789012",
        "Tags": { "environment": "pci" },
        "VpcId": "vpc-abc111222333",
      }
  - Name: Security Group Does Not Restrict Traffic Leaving CDE
    ExpectedResult: false
    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,
                  },
                ],
            },
          ],
        "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": "pci" },
        "VpcId": "vpc-abc111222333",
      }

Detection logic

Rule logic imperative Python

from ipaddress import ip_network
def policy(resource):
    for permission in resource["IpPermissionsEgress"] or []:
        for ip_range in permission["IpRanges"] or []:
            if ip_range["CidrIp"] == "0.0.0.0/0" or not ip_network(ip_range["CidrIp"]).is_private:
                return False
        for ip_range in permission["Ipv6Ranges"] or []:
            if ip_range["CidrIpv6"] == "::/0" or not ip_network(ip_range["CidrIpv6"]).is_private:
                return False
    return True

The parser cannot express this rule's logic as a field filter; the imperative Python above is the detection.

`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)

AWS Security Group Restricts Traffic Leaving CDE

MITRE ATT&CK coverage

Rule body yaml

Detection logic

Rule logic imperative Python

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