AWS IAM Backdoor Users Keys

Status: test
Severity: medium
Log source: product aws, service cloudtrail
Author: faloker
Source: github.com/SigmaHQ/sigma

Detects AWS API key creation for a user by another user. Backdoored users can be used to obtain persistence in the AWS environment. Also with this alert, you can detect a flow of AWS keys in your org.

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1098` Account Manipulation
Privilege Escalation	`T1098` Account Manipulation

Event coverage

Provider	Event
AWS-iam	CreateAccessKey

Rules detecting the same action

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

AWS IAM S3Browser User or AccessKey Creation (Sigma)
AWS IAM Sensitive Operations via Lambda Execution Role (Elastic)
AWS IAM User Created Access Keys For Another User (Elastic)
AWS Sensitive IAM Operations Performed via CloudShell (Elastic)
AWS User API Key Created (Panther)
High-Risk Cross-Cloud User Impersonation (Kusto)
IAM Access Key Created (Sigma)
IAM Access Key Creation Attempt (Sigma)

Rule body yaml

title: AWS IAM Backdoor Users Keys
id: 0a5177f4-6ca9-44c2-aacf-d3f3d8b6e4d2
status: test
description: |
  Detects AWS API key creation for a user by another user.
  Backdoored users can be used to obtain persistence in the AWS environment.
  Also with this alert, you can detect a flow of AWS keys in your org.
references:
    - https://github.com/RhinoSecurityLabs/pacu/blob/866376cd711666c775bbfcde0524c817f2c5b181/pacu/modules/iam__backdoor_users_keys/main.py
author: faloker
date: 2020-02-12
modified: 2022-10-09
tags:
    - attack.persistence
    - attack.privilege-escalation
    - attack.t1098
logsource:
    product: aws
    service: cloudtrail
detection:
    selection_source:
        eventSource: iam.amazonaws.com
        eventName: CreateAccessKey
    filter:
        userIdentity.arn|contains: responseElements.accessKey.userName
    condition: selection_source and not filter
falsepositives:
    - Adding user keys to their own accounts (the filter cannot cover all possible variants of user naming)
    - AWS API keys legitimate exchange workflows
level: medium

Stages and Predicates

Stage 0: `condition`

selection_source and not filter

Stage 1: `selection_source`

selection_source:
    eventSource: iam.amazonaws.com
    eventName: CreateAccessKey

Stage 2: `not filter`

filter:
    userIdentity.arn|contains: responseElements.accessKey.userName

Exclusions

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

Field	Kind	Excluded values
`userIdentity.arn`	match	`responseElements.accessKey.userName`

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	`CreateAccessKey`
`eventSource`	eq	`iam.amazonaws.com`

`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 IAM Backdoor Users Keys

MITRE ATT&CK coverage

Event coverage

Rules detecting the same action

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection_source`

Stage 2: `not filter`

Exclusions

Indicators

Keyboard shortcuts

Search operators

AWS IAM Backdoor Users Keys

MITRE ATT&CK coverage

Event coverage

Rules detecting the same action

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection_source

Stage 2: not filter

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection_source`

Stage 2: `not filter`