AWS AMI Sharing

Severity: high
Tags: AWS, Panther, Panther Enterprise, Exfiltration:Transfer Data to Cloud Account
Reference: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/sharing-amis.html
Source: github.com/panther-labs/panther-analysis

This policy ensures that AMIs you have created are not configured to allow public access, which could result in accidental data loss. AMI's that you use but do not own are not evaluated by this policy.

MITRE ATT&CK coverage

Tactic	Techniques
Exfiltration	`T1537` Transfer Data to Cloud Account

Rule body yaml

AnalysisType: policy
Filename: aws_ami_private.py
PolicyID: "AWS.AMI.Private"
DisplayName: "AWS AMI Sharing"
Enabled: true
ResourceTypes:
  - AWS.EC2.AMI
Tags:
  - AWS
  - Panther
  - Panther Enterprise
  - Exfiltration:Transfer Data to Cloud Account
Reports:
  MITRE ATT&CK:
    - TA0010:T1537
Severity: High
Description: >
  This policy ensures that AMIs you have created are not configured to allow public access, which could result in accidental data loss. AMI's that you use but do not own are not evaluated by this policy.
Runbook: >
  Immediately remove public access from the AMI until you can determine whether that setting is intentional
Reference: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/sharing-amis.html
Tests:
  - Name: Private AMI
    ExpectedResult: true
    Resource:
      {
        "AccountId": "123456789012",
        "Region": "us-west-2",
        "ARN": "arn:aws:ec2:us-west-2:123456789012:image/ami-abc234",
        "ID": "ami-abc234",
        "Name": "ubuntu/image",
        "Tags": {},
        "ResourceID": "arn:aws:ec2:us-west-2:123456789012:image/ami-abc234",
        "ResourceType": "AWS.EC2.AMI",
        "TimeCreated": "2011-11-04T12:34:17.000Z",
        "Architecture": "x86_64",
        "BlockDeviceMappings": [],
        "Description": null,
        "EnaSupport": null,
        "Hypervisor": "xen",
        "ImageId": "ami-abc234",
        "ImageLocation": "ubuntu-us-west-2/kernels/ubuntu.xml",
        "ImageOwnerAlias": null,
        "ImageType": "ramdisk",
        "KernelId": null,
        "OwnerId": "123456789012",
        "Platform": null,
        "ProductCodes": null,
        "Public": false,
        "RamdiskId": null,
        "RootDeviceName": null,
        "RootDeviceType": "instance-store",
        "SriovNetSupport": null,
        "State": "available",
        "StateReason": null,
        "VirtualizationType": "paravirtual",
      }
  - Name: Public AMI
    ExpectedResult: false
    Resource:
      {
        "AccountId": "123456789012",
        "Region": "us-west-2",
        "ARN": "arn:aws:ec2:us-west-2:123456789012:image/ami-abc234",
        "ID": "ami-abc234",
        "Name": "ubuntu/image",
        "Tags": {},
        "ResourceID": "arn:aws:ec2:us-west-2:123456789012:image/ami-abc234",
        "ResourceType": "AWS.EC2.AMI",
        "TimeCreated": "2011-11-04T12:34:17.000Z",
        "Architecture": "x86_64",
        "BlockDeviceMappings": [],
        "Description": null,
        "EnaSupport": null,
        "Hypervisor": "xen",
        "ImageId": "ami-abc234",
        "ImageLocation": "ubuntu-us-west-2/kernels/ubuntu.xml",
        "ImageOwnerAlias": null,
        "ImageType": "ramdisk",
        "KernelId": null,
        "OwnerId": "123456789012",
        "Platform": null,
        "ProductCodes": null,
        "Public": true,
        "RamdiskId": null,
        "RootDeviceName": null,
        "RootDeviceType": "instance-store",
        "SriovNetSupport": null,
        "State": "available",
        "StateReason": null,
        "VirtualizationType": "paravirtual",
      }

Detection logic

Condition

not (ImageOwnerAlias in ["amazon", "microsoft"] or AccountId cross_field_compare "OwnerId" or Public is_null)

Exclusions

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

Field	Kind	Excluded values
`AccountId`	cross_field_compare	`OwnerId`
`ImageOwnerAlias`	in	`amazon`, `microsoft`
`Public`	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)