AWS STS GetSessionToken by IAM User

Status: Experimental
Severity: low
Log types: AWS.CloudTrail
Tags: AWS, AWS STS, Lateral Movement:Use Alternate Authentication Material, Privilege Escalation:Abuse Elevation Control Mechanism
Reference: https://docs.aws.amazon.com/STS/latest/APIReference/API_GetSessionToken.html
Source: github.com/panther-labs/panther-analysis

Detects an IAM user calling STS GetSessionToken to obtain temporary credentials. Attackers who have compromised long-term IAM credentials may use GetSessionToken to generate short-lived session tokens for lateral movement or to bypass IP-based policies that apply only to long-term credentials.

MITRE ATT&CK coverage

Tactic	Techniques
Privilege Escalation	`T1548` Abuse Elevation Control Mechanism
Lateral Movement	`T1550.001` Use Alternate Authentication Material: Application Access Token

Rules detecting the same action

Other rules on this platform that filter on the same API call or operation.

AWS Authentication from CrowdStrike Unmanaged Device (crowdstrike_fdrevent table) (Panther)
AWS STS GetSessionToken Misuse (Sigma)
AWS STS GetSessionToken Usage (Elastic)

Rule body yaml

AnalysisType: rule
Filename: aws_sts_getsessiontoken_misuse.py
RuleID: "AWS.STS.GetSessionToken.Misuse"
DisplayName: "AWS STS GetSessionToken by IAM User"
Enabled: true
LogTypes:
  - AWS.CloudTrail
Tags:
  - AWS
  - AWS STS
  - Lateral Movement:Use Alternate Authentication Material
  - Privilege Escalation:Abuse Elevation Control Mechanism
Reports:
  MITRE ATT&CK:
    - TA0008:T1550.001
    - TA0004:T1548
Status: Experimental
Severity: Low
Description: >
  Detects an IAM user calling STS GetSessionToken to obtain temporary credentials.
  Attackers who have compromised long-term IAM credentials may use GetSessionToken
  to generate short-lived session tokens for lateral movement or to bypass IP-based
  policies that apply only to long-term credentials.
Runbook: |
  1. Query CloudTrail for all API calls by userIdentity:arn in the 6 hours before and after this alert to establish what the session token was used for
  2. Check if sourceIPAddress is associated with known corporate network ranges, VPN endpoints, or cloud provider IP ranges
  3. Find other alerts for this userIdentity:userName in the past 30 days to determine if GetSessionToken usage is part of normal workflow
Reference: https://docs.aws.amazon.com/STS/latest/APIReference/API_GetSessionToken.html
SummaryAttributes:
  - userAgent
  - sourceIpAddress
  - recipientAccountId
  - p_any_aws_arns
DedupPeriodMinutes: 60
Threshold: 1
Tests:
  - Name: GetSessionToken by IAM User
    ExpectedResult: true
    Log:
      {
        "awsRegion": "us-east-1",
        "eventID": "abc-123",
        "eventName": "GetSessionToken",
        "eventSource": "sts.amazonaws.com",
        "eventTime": "2024-01-15T10:30:00Z",
        "eventType": "AwsApiCall",
        "eventVersion": "1.08",
        "recipientAccountId": "123456789012",
        "requestID": "req-123",
        "sourceIPAddress": "203.0.113.50",
        "userAgent": "aws-cli/2.15.0",
        "userIdentity": {
          "accessKeyId": "AKIAIOSFODNN7EXAMPLE",
          "accountId": "123456789012",
          "arn": "arn:aws:iam::123456789012:user/example-user",
          "principalId": "AIDACKCEVSQ6C2EXAMPLE",
          "type": "IAMUser",
          "userName": "example-user"
        }
      }
  - Name: GetSessionToken Failed
    ExpectedResult: false
    Log:
      {
        "awsRegion": "us-east-1",
        "errorCode": "AccessDenied",
        "eventName": "GetSessionToken",
        "eventSource": "sts.amazonaws.com",
        "eventTime": "2024-01-15T10:30:00Z",
        "eventType": "AwsApiCall",
        "recipientAccountId": "123456789012",
        "sourceIPAddress": "203.0.113.50",
        "userIdentity": {
          "type": "IAMUser",
          "userName": "example-user"
        }
      }
  - Name: GetSessionToken by Assumed Role
    ExpectedResult: false
    Log:
      {
        "awsRegion": "us-east-1",
        "eventName": "GetSessionToken",
        "eventSource": "sts.amazonaws.com",
        "eventTime": "2024-01-15T10:30:00Z",
        "eventType": "AwsApiCall",
        "recipientAccountId": "123456789012",
        "sourceIPAddress": "10.0.0.1",
        "userIdentity": {
          "type": "AssumedRole",
          "arn": "arn:aws:sts::123456789012:assumed-role/MyRole/session"
        }
      }
  - Name: Unrelated STS Event
    ExpectedResult: false
    Log:
      {
        "awsRegion": "us-east-1",
        "eventName": "AssumeRole",
        "eventSource": "sts.amazonaws.com",
        "eventTime": "2024-01-15T10:30:00Z",
        "eventType": "AwsApiCall",
        "recipientAccountId": "123456789012",
        "sourceIPAddress": "10.0.0.1",
        "userIdentity": {
          "type": "IAMUser",
          "userName": "example-user"
        }
      }

Detection logic

Condition

not (errorCode is_not_null or errorMessage is_not_null)
eventSource eq "sts.amazonaws.com"
eventName eq "GetSessionToken"
userIdentity.type eq "IAMUser"

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)

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
`eventName`	eq	`GetSessionToken`
`eventSource`	eq	`sts.amazonaws.com`
`userIdentity.type`	eq	`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	Source
`eventName`
`eventSource`
`awsRegion`
`recipientAccountId`
`sourceIPAddress`
`userAgent`
`userIdentity`
`userName`	`userIdentity.userName`

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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)