IAM User Creation Attempt

Status: test
Severity: medium
Log source: product aws, service cloudtrail
Author: nishikawaakira (@nishikawaakira)
Source: github.com/Yamato-Security/suzaku-rules

Detects a failed attempt to create an IAM user (AccessDenied). Even though the attempt failed, it indicates the attacker has valid credentials and is attempting persistence via IAM user creation.

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1136.003` Create Account: Cloud Account

Telemetry coverage

Platform	Record / event type
AWS	CloudTrail event `CreateUser`: Creates a new IAM user in the AWS account with a specified user name.

Rules detecting the same action

These rules filter on the same operation.

AWS IAM Create User via Assumed Role on EC2 Instance (Elastic)
AWS IAM S3Browser User or AccessKey Creation (Sigma)
AWS IAM Sensitive Operations via Lambda Execution Role (Elastic)
AWS Sensitive IAM Operations Performed via CloudShell (Elastic)
High-Risk Cross-Cloud User Impersonation (Kusto)
IAM User Created (Sigma)

Rule body

title: IAM User Creation Attempt
id: 8f3a7b2c-1d4e-5f6a-9b0c-2e3d4f5a6b7d
status: test
description: |
    Detects a failed attempt to create an IAM user (AccessDenied).
    Even though the attempt failed, it indicates the attacker has valid
    credentials and is attempting persistence via IAM user creation.
references:
    - https://attack.mitre.org/techniques/T1136/003/
    - https://docs.aws.amazon.com/IAM/latest/APIReference/API_CreateUser.html
author: nishikawaakira (@nishikawaakira)
date: 2026-05-03
modified: 2026-05-29
tags:
    - attack.persistence
    - attack.t1136.003
logsource:
    product: aws
    service: cloudtrail
detection:
    selection:
        eventSource: iam.amazonaws.com
        eventName: CreateUser
        errorCode: AccessDenied
    condition: selection
falsepositives:
level: medium

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    eventSource: iam.amazonaws.com
    eventName: CreateUser
    errorCode: AccessDenied

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`errorCode`	eq	`AccessDenied`	`field:"aws::errorCode" kind:eq value:"AccessDenied"`
`eventName`	eq	`CreateUser`	`field:"aws::eventName" kind:eq value:"CreateUser"`
`eventSource`	eq	`iam.amazonaws.com`	`field:"aws::eventSource" kind:eq value:"iam.amazonaws.com"`