IAM Assume Role Blocklist Ignored

Severity: high
Log types: AWS.CloudTrail
Tags: AWS, Configuration Required, Identity and Access Management, Privilege Escalation:Abuse Elevation Control Mechanism
Reference: https://docs.aws.amazon.com/IAM/latest/UserGuide/access_policies_boundaries.html
Source: github.com/panther-labs/panther-analysis

A user assumed a role that was explicitly blocklisted for manual user assumption.

MITRE ATT&CK coverage

Tactic	Techniques
Privilege Escalation	`T1548` Abuse Elevation Control Mechanism

Rule body yaml

AnalysisType: rule
Filename: aws_iam_assume_role_blocklist_ignored.py
RuleID: "AWS.CloudTrail.IAMAssumeRoleBlacklistIgnored"
DisplayName: "IAM Assume Role Blocklist Ignored"
Enabled: false
LogTypes:
  - AWS.CloudTrail
Tags:
  - AWS
  - Configuration Required
  - Identity and Access Management
  - Privilege Escalation:Abuse Elevation Control Mechanism
Reports:
  MITRE ATT&CK:
    - TA0004:T1548
Severity: High
Description: >
  A user assumed a role that was explicitly blocklisted for manual user assumption.
Runbook: >
  Verify that this was an approved assume role action. If not, consider revoking the access immediately and updating the AssumeRolePolicyDocument to prevent this from happening again.
Reference: https://docs.aws.amazon.com/IAM/latest/UserGuide/access_policies_boundaries.html
SummaryAttributes:
  - userAgent
  - sourceIpAddress
  - recipientAccountId
  - p_any_aws_arns
Tests:
  - Name: IAM Blocklisted Role Assumed
    ExpectedResult: true
    Log:
      {
        "awsRegion": "us-east-1",
        "eventID": "1111",
        "eventName": "AssumeRole",
        "eventSource": "sts.amazonaws.com",
        "eventTime": "2019-01-01T00:00:00Z",
        "eventType": "AwsApiCall",
        "eventVersion": "1.05",
        "recipientAccountId": "123456789012",
        "requestID": "1111",
        "requestParameters":
          {
            "durationSeconds": 900,
            "roleArn": "arn:aws:iam::123456789012:role/FullAdminRole",
            "roleSessionName": "1111",
          },
        "resources":
          [
            {
              "ARN": "arn:aws:iam::123456789012:role/FullAdminRole",
              "accountId": "123456789012",
              "type": "AWS::IAM::Role",
            },
          ],
        "responseElements":
          {
            "assumedRoleUser":
              {
                "arn": "arn:aws:sts::123456789012:assumed-role/FullAdminRole/1111",
                "assumedRoleId": "ABCD:1111",
              },
            "credentials":
              {
                "accessKeyId": "1111",
                "expiration": "Jan 01, 2019 0:00:00 PM",
                "sessionToken": "1111",
              },
          },
        "sharedEventID": "1111",
        "sourceIPAddress": "111.111.111.111",
        "userAgent": "aws-sdk-go/1.4.14 (go1.11.4; darwin; amd64)",
        "userIdentity":
          {
            "accesKeyId": "1111",
            "accessKeyId": "1111",
            "accountId": "123456789012",
            "arn": "arn:aws:iam::123456789012:user/example-user",
            "principalId": "1111",
            "sessionContext":
              {
                "attributes":
                  {
                    "creationDate": "2019-01-01T00:00:00Z",
                    "mfaAuthenticated": "true",
                  },
              },
            "type": "IAMUser",
            "userName": "example-user",
          },
      }
  - Name: IAM Non Blocklisted Role Assumed
    ExpectedResult: false
    Log:
      {
        "awsRegion": "us-east-1",
        "eventID": "1111",
        "eventName": "AssumeRole",
        "eventSource": "sts.amazonaws.com",
        "eventTime": "2019-01-01T00:00:00Z",
        "eventType": "AwsApiCall",
        "eventVersion": "1.05",
        "recipientAccountId": "123456789012",
        "requestID": "1111",
        "requestParameters":
          {
            "durationSeconds": 900,
            "roleArn": "arn:aws:iam::123456789012:role/example-role",
            "roleSessionName": "1111",
          },
        "resources":
          [
            {
              "ARN": "arn:aws:iam::123456789012:role/example-role",
              "accountId": "123456789012",
              "type": "AWS::IAM::Role",
            },
          ],
        "responseElements":
          {
            "assumedRoleUser":
              {
                "arn": "arn:aws:sts::123456789012:assumed-role/example-role/1111",
                "assumedRoleId": "ABCD:1111",
              },
            "credentials":
              {
                "accessKeyId": "1111",
                "expiration": "Jan 01, 2019 0:00:00 PM",
                "sessionToken": "1111",
              },
          },
        "sharedEventID": "1111",
        "sourceIPAddress": "111.111.111.111",
        "userAgent": "aws-sdk-go/1.4.14 (go1.11.4; darwin; amd64)",
        "userIdentity":
          {
            "accesKeyId": "1111",
            "accessKeyId": "1111",
            "accountId": "123456789012",
            "arn": "arn:aws:iam::123456789012:user/example-user",
            "principalId": "1111",
            "sessionContext":
              {
                "attributes":
                  {
                    "creationDate": "2019-01-01T00:00:00Z",
                    "mfaAuthenticated": "true",
                  },
              },
            "type": "IAMUser",
            "userName": "example-user",
          },
      }
  - Name: Error Assuming IAM Blocked Role
    ExpectedResult: false
    Log:
      {
        "awsRegion": "us-east-1",
        "errorCode": "ExpiredToken",
        "eventID": "1111",
        "eventName": "AssumeRole",
        "eventSource": "sts.amazonaws.com",
        "eventTime": "2019-01-01T00:00:00Z",
        "eventType": "AwsApiCall",
        "eventVersion": "1.05",
        "recipientAccountId": "123456789012",
        "requestID": "1111",
        "requestParameters":
          {
            "durationSeconds": 900,
            "roleArn": "arn:aws:iam::123456789012:role/FullAdminRole",
            "roleSessionName": "1111",
          },
        "resources":
          [
            {
              "ARN": "arn:aws:iam::123456789012:role/FullAdminRole",
              "accountId": "123456789012",
              "type": "AWS::IAM::Role",
            },
          ],
        "responseElements":
          {
            "assumedRoleUser":
              {
                "arn": "arn:aws:sts::123456789012:assumed-role/FullAdminRole/1111",
                "assumedRoleId": "ABCD:1111",
              },
            "credentials":
              {
                "accessKeyId": "1111",
                "expiration": "Jan 01, 2019 0:00:00 PM",
                "sessionToken": "1111",
              },
          },
        "sharedEventID": "1111",
        "sourceIPAddress": "111.111.111.111",
        "userAgent": "aws-sdk-go/1.4.14 (go1.11.4; darwin; amd64)",
        "userIdentity":
          {
            "accesKeyId": "1111",
            "accessKeyId": "1111",
            "accountId": "123456789012",
            "arn": "arn:aws:iam::123456789012:user/example-user",
            "principalId": "1111",
            "sessionContext":
              {
                "attributes":
                  {
                    "creationDate": "2019-01-01T00:00:00Z",
                    "mfaAuthenticated": "true",
                  },
              },
            "type": "IAMUser",
            "userName": "example-user",
          },
      }

Detection logic

Condition

not (errorCode is_not_null or errorMessage is_not_null or eventName ne "AssumeRole")
userIdentity.type in ["IAMUser", "FederatedUser"]
requestParameters.roleArn in "arn:aws:iam::123456789012:role/FullAdminRole"

Exclusions

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

Field	Kind	Excluded values
`errorCode`	is_not_null	(no value, null check)
`errorMessage`	is_not_null	(no value, null check)
`eventName`	ne	`AssumeRole`

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
`requestParameters.roleArn`	in	`arn:aws:iam::123456789012:role/FullAdminRole`
`userIdentity.type`	in	`FederatedUser` `IAMUser`

Output fields

Fields the rule emits when it matches. Chronicle authors list these in the outcome block; they appear on the detection and $risk_score drives alerting. Sentinel / Defender XDR rules build them up through project / summarize / extend stages. Sentinel maps these into alert fields via entityMappings and customDetails; Defender XDR custom detections surface them as alert fields directly.

Field
`eventName`
`eventSource`
`awsRegion`
`recipientAccountId`
`sourceIPAddress`
`userAgent`
`userIdentity`

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
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`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
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`Enter`	Open highlighted result
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`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)