AWS CloudTrail: S3 Browser Creates IAM User or Access Key

Alerts on CloudTrail IAM CreateUser/CreateAccessKey actions initiated by a "S3 Browser" user agent.

FreeReviewedSigma · High · v5

Product: aws
Service: cloudtrail
Author: daniel.bohannon@permiso.io (@danielhbohannon) (SigmaHQ), DRL 1.1
Published: 2023-05-17
Updated: 2026-07-31

ATT&CK techniques

Initial Access → Defense Evasion

Recon
Resource Dev
Initial Access
- T1078.004Cloud Accounts
Execution
- T1059.009Cloud API
Persistence
- T1078.004Cloud Accounts
Priv Esc
- T1078.004Cloud Accounts
Defense Evasion
- T1078.004Cloud Accounts
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags AWS CloudTrail events where IAM users or access keys are created and the request user agent contains "S3 Browser". Creating IAM credentials is a common step for establishing persistence and enabling authenticated access to AWS resources. The detection relies on CloudTrail IAM CreateUser and CreateAccessKey events correlated with the client user agent string.

Reporting behind it

Related detections9 linkedT1078.004 — drag to rearrange

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Suspicious M365 Password Spraying via Azure PowerShell AppId from Quad7 Botnet

Suspicious AWS Instance Access or Export via SSH Key or Export Task

Suspicious Azure OpenAI Model Enumeration and Deployment Creation (via azure)

Suspicious Azure Cognitive Services Account Key Enumeration via ListKeys (via azure)

AWS CloudTrail: S3 Browser Creates IAM User or Access Key

Pivot detection · T1078.004 · 9 related

Changelog

v5
Candidate ingested via manual entry.2026-07-31
v4
Candidate ingested via manual entry.2026-07-31
v3
Candidate ingested via manual entry.2026-07-31
v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

aws-cloudtrail-s3-browser-creating-iam-user-or-access-key-db014773

title: "AWS CloudTrail: S3 Browser Creates IAM User or Access Key"
id: 52c64136-c7c0-457a-8c3a-5aca798566d6
status: test
description: This rule flags AWS CloudTrail events where IAM users or access keys are created and the request user agent contains "S3 Browser". Creating IAM credentials is a common step for establishing persistence and enabling authenticated access to AWS resources. The detection relies on CloudTrail IAM CreateUser and CreateAccessKey events correlated with the client user agent string.
references:
  - https://permiso.io/blog/s/unmasking-guivil-new-cloud-threat-actor
  - https://github.com/SigmaHQ/sigma/blob/master/rules/cloud/aws/cloudtrail/aws_iam_s3browser_user_or_accesskey_creation.yml
author: daniel.bohannon@permiso.io (@danielhbohannon), Huntrule Team
date: 2023-05-17
tags:
  - attack.privilege-escalation
  - attack.execution
  - attack.persistence
  - attack.initial-access
  - attack.stealth
  - attack.t1059.009
  - attack.t1078.004
logsource:
  product: aws
  service: cloudtrail
detection:
  selection:
    eventSource: iam.amazonaws.com
    eventName:
      - CreateUser
      - CreateAccessKey
    userAgent|contains: S3 Browser
  condition: selection
falsepositives:
  - Valid usage of S3 Browser for IAM User and/or AccessKey creation
level: high
license: DRL-1.1
related:
  - id: db014773-d9d9-4792-91e5-133337c0ffee
    type: derived

Convert

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