Files
sigma-rules/rules
Isai cd003fc9a7 [New Rule] AWS CloudTrail Log Evasion (#4788)
* [New Rule] AWS CloudTrail Log Evasion

Identifies the evasion of cloudtrail logging for IAM actions involving policy creation, modification or attachment. When making certain policy-related API calls, an adversary may pad the associated policy document with whitespaces to trigger CloudTrail’s logging size constraints, resulting in incomplete logging where critical details about the policy are omitted. By exploiting this gap, threat actors can bypass monitoring performed through CloudTrail and can effectively obscure unauthorized changes. This rule looks for IAM API calls with the requestParameters property containing reason:”requestParameters too large” and omitted:true.

This is a known gap in AWS with no immediate remediation steps. While the size constraint issue affects additional services, IAM policy-related API calls are the only that pose a security risk which is why this rule is scoped specifically to `event.provider: iam.amazonaws.com`.  For additional background on the evasion technique refer to Permisso's [research](https://permiso.io/blog/cloudtrail-logging-evasion-where-policy-size-matters).

* aligning IG and rule name

* added investigation fields

added investigation fields

* change severity

* updating pyproject version
2025-06-17 13:58:26 -04:00
..
2025-03-26 11:04:14 -04:00

rules/

Rules within this folder are organized by solution or platform. The structure is flattened out, because nested file hierarchies are hard to navigate and find what you're looking for. Each directory contains several .toml files, and the primary ATT&CK tactic is included in the file name when it's relevant (i.e. windows/execution_via_compiled_html_file.toml)

folder description
. Root directory where rules are stored
apm/ Rules that use Application Performance Monitoring (APM) data sources
cross-platform/ Rules that apply to multiple platforms, such as Windows and Linux
integrations/ Rules organized by Fleet integration
linux/ Rules for Linux or other Unix based operating systems
macos/ Rules for macOS
ml/ Rules that use machine learning jobs (ML)
network/ Rules that use network data sources
promotions/ Rules that promote external alerts into detection engine alerts
windows/ Rules for the Microsoft Windows Operating System

Integration specific rules are stored in the integrations/ directory:

folder integration
aws/ Amazon Web Services (AWS)
azure/ Microsoft Azure
cyberarkpas/ Cyber Ark Privileged Access Security
endpoint/ Elastic Endpoint Security
gcp/ Google Cloud Platform (GCP)
google_workspace/ Google Workspace (formerly GSuite)
o365/ Microsoft Office
okta/ Oka