AWS IMDS Credential Usage Outside Expected Services

Status: Experimental
Severity: high
Log types: AWS.CloudTrail
Tags: AWS, AWS STS, Privilege Escalation:Valid Accounts, Defense Evasion:Valid Accounts
Reference: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/configuring-instance-metadata-service.html
Source: github.com/panther-labs/panther-analysis

Detects when an EC2 instance identity (credentials obtained via IMDS) is used to make API calls outside of expected internal AWS services like SSM. This indicates that IMDS credentials may have been exfiltrated from a compromised instance and are being used externally for lateral movement or privilege escalation.

MITRE ATT&CK coverage

Tactic	Techniques
Privilege Escalation	`T1078.004` Valid Accounts: Cloud Accounts
Stealth	`T1078.004` Valid Accounts: Cloud Accounts

Rule body yaml

AnalysisType: rule
Filename: aws_imds_credential_exfiltration.py
RuleID: "AWS.CloudTrail.IMDSCredentialExfiltration"
DisplayName: "AWS IMDS Credential Usage Outside Expected Services"
Enabled: true
LogTypes:
  - AWS.CloudTrail
Tags:
  - AWS
  - AWS STS
  - Privilege Escalation:Valid Accounts
  - Defense Evasion:Valid Accounts
Reports:
  MITRE ATT&CK:
    - TA0004:T1078.004
    - TA0005:T1078.004
Status: Experimental
Severity: High
Description: >
  Detects when an EC2 instance identity (credentials obtained via IMDS) is used to
  make API calls outside of expected internal AWS services like SSM. This indicates
  that IMDS credentials may have been exfiltrated from a compromised instance and
  are being used externally for lateral movement or privilege escalation.
Runbook: |
  1. Query CloudTrail for all API calls by userIdentity:arn in the 24 hours before and after this alert to identify the full scope of actions taken with the exfiltrated instance credentials
  2. Check if sourceIPAddress is external to AWS or outside the expected VPC CIDR ranges for the EC2 instance associated with this role
  3. Find all other alerts associated with this userIdentity:arn or sourceIPAddress in the past 7 days to assess whether this is part of a broader compromise campaign
Reference: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/configuring-instance-metadata-service.html
SummaryAttributes:
  - userAgent
  - sourceIpAddress
  - recipientAccountId
  - p_any_aws_arns
DedupPeriodMinutes: 60
Threshold: 1
Tests:
  - Name: IMDS Credentials Used From Public IP
    ExpectedResult: true
    Log:
      {
        "awsRegion": "us-east-1",
        "eventName": "DescribeInstances",
        "eventSource": "ec2.amazonaws.com",
        "eventTime": "2024-01-15T10:30:00Z",
        "eventType": "AwsApiCall",
        "recipientAccountId": "123456789012",
        "sourceIPAddress": "45.33.32.156",
        "userAgent": "aws-cli/2.15.0",
        "userIdentity": {
          "accessKeyId": "ASIAIOSFODNN7EXAMPLE",
          "accountId": "123456789012",
          "arn": "arn:aws:sts::123456789012:assumed-role/MyAppRole/i-0abcdef1234567890",
          "principalId": "AROAEXAMPLE:i-0abcdef1234567890",
          "type": "AssumedRole",
          "sessionContext": {
            "sessionIssuer": {
              "type": "Role",
              "arn": "arn:aws:iam::123456789012:role/MyAppRole"
            }
          }
        }
      }
  - Name: Normal EC2 Workload From Private IP
    ExpectedResult: false
    Log:
      {
        "awsRegion": "us-east-1",
        "eventName": "PutObject",
        "eventSource": "s3.amazonaws.com",
        "eventTime": "2024-01-15T10:30:00Z",
        "eventType": "AwsApiCall",
        "recipientAccountId": "123456789012",
        "sourceIPAddress": "10.0.1.50",
        "userAgent": "aws-sdk-java/2.20.0",
        "userIdentity": {
          "arn": "arn:aws:sts::123456789012:assumed-role/MyAppRole/i-0abcdef1234567890",
          "type": "AssumedRole"
        }
      }
  - Name: AWS Service Hostname as Source IP
    ExpectedResult: false
    Log:
      {
        "awsRegion": "us-east-1",
        "eventName": "Decrypt",
        "eventSource": "kms.amazonaws.com",
        "eventTime": "2024-01-15T10:30:00Z",
        "eventType": "AwsApiCall",
        "recipientAccountId": "123456789012",
        "sourceIPAddress": "cloudformation.amazonaws.com",
        "userIdentity": {
          "arn": "arn:aws:sts::123456789012:assumed-role/MyAppRole/i-0abcdef1234567890",
          "type": "AssumedRole"
        }
      }
  - Name: Legitimate SSM Activity
    ExpectedResult: false
    Log:
      {
        "awsRegion": "us-east-1",
        "eventName": "UpdateInstanceInformation",
        "eventSource": "ssm.amazonaws.com",
        "eventTime": "2024-01-15T10:30:00Z",
        "eventType": "AwsApiCall",
        "recipientAccountId": "123456789012",
        "sourceIPAddress": "10.0.1.50",
        "userAgent": "amazon-ssm-agent/3.2.0",
        "userIdentity": {
          "arn": "arn:aws:sts::123456789012:assumed-role/MyAppRole/i-0abcdef1234567890",
          "type": "AssumedRole"
        }
      }
  - Name: AWS Internal Source IP
    ExpectedResult: false
    Log:
      {
        "awsRegion": "us-east-1",
        "eventName": "SendHeartbeat",
        "eventSource": "ec2messages.amazonaws.com",
        "eventTime": "2024-01-15T10:30:00Z",
        "eventType": "AwsApiCall",
        "recipientAccountId": "123456789012",
        "sourceIPAddress": "AWS Internal",
        "userAgent": "amazon-ssm-agent/3.2.0",
        "userIdentity": {
          "arn": "arn:aws:sts::123456789012:assumed-role/MyAppRole/i-0abcdef1234567890",
          "type": "AssumedRole"
        }
      }
  - Name: RegisterManagedInstance Event
    ExpectedResult: false
    Log:
      {
        "awsRegion": "us-east-1",
        "eventName": "RegisterManagedInstance",
        "eventSource": "ec2.amazonaws.com",
        "eventTime": "2024-01-15T10:30:00Z",
        "eventType": "AwsApiCall",
        "recipientAccountId": "123456789012",
        "sourceIPAddress": "10.0.1.50",
        "userIdentity": {
          "arn": "arn:aws:sts::123456789012:assumed-role/MyAppRole/i-0abcdef1234567890",
          "type": "AssumedRole"
        }
      }
  - Name: Non-Instance Role
    ExpectedResult: false
    Log:
      {
        "awsRegion": "us-east-1",
        "eventName": "DescribeInstances",
        "eventSource": "ec2.amazonaws.com",
        "eventTime": "2024-01-15T10:30:00Z",
        "eventType": "AwsApiCall",
        "recipientAccountId": "123456789012",
        "sourceIPAddress": "45.33.32.156",
        "userAgent": "aws-cli/2.15.0",
        "userIdentity": {
          "arn": "arn:aws:sts::123456789012:assumed-role/MyCustomRole/session",
          "type": "AssumedRole"
        }
      }

Detection logic

Condition

eventSource not in "ssm.amazonaws.com"
eventName not in "RegisterManagedInstance"
sourceIPAddress not in "AWS Internal"

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
`eventName`	eq	`RegisterManagedInstance`
`eventSource`	eq	`ssm.amazonaws.com`
`sourceIPAddress`	eq	`AWS Internal`

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	Source
`eventName`
`eventSource`
`awsRegion`
`recipientAccountId`
`sourceIPAddress`
`userAgent`
`userIdentity`
`arn`	`userIdentity.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)