Detects ShimRatReporter

Hunt Hypothesis

This hypothesis posits that adversaries are leveraging the ShimRatReporter utility to establish persistent footholds or exfiltrate data within Azure environments by mimicking legitimate reporting processes. Proactive hunting is essential because this low-severity activity often evades standard alerting thresholds, requiring manual correlation of process lineage and network connections to uncover stealthy lateral movement or command-and-control communications.

YARA Rule

rule shimratreporter: RAT
{
 meta:
  description = "Detects ShimRatReporter"
  author = "Yonathan Klijnsma ([email protected])"
  date = "20/11/2015"
  ref = "https://blog.fox-it.com/2016/06/15/mofang-a-politically-motivated-information-stealing-adversary/"


 strings:
  $IpInfo = "IP-INFO"
  $NetworkInfo = "Network-INFO"
  $OsInfo = "OS-INFO"
  $ProcessInfo = "Process-INFO"
  $BrowserInfo = "Browser-INFO"
  $QueryUserInfo = "QueryUser-INFO"
  $UsersInfo = "Users-INFO"
  $SoftwareInfo = "Software-INFO"
  $AddressFormat = "%02X-%02X-%02X-%02X-%02X-%02X"
  $proxy_str = "(from environment) = %s"

  $netuserfun = "NetUserEnum"
  $networkparams = "GetNetworkParams"

 condition:
  all of them
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

• Microsoft Defender for Endpoint — Custom indicators / advanced hunting
• Email Gateway — Attachment scanning
• File Share Monitoring — Periodic scanning of shared drives
• YARA CLI — Manual threat hunting on endpoints

This rule contains 12 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 4 specific false positive scenarios for the ShimRatReporter detection rule in an enterprise environment, along with suggested filters or exclusions:

• Scenario: Scheduled Antivirus Definition Updates via Microsoft Endpoint Configuration Manager (MECM/SCCM)

  • Context: During nightly maintenance windows, SCCM pushes updated definition packages to endpoints. The ShimRatReporter process is triggered by the Windows Update Agent to validate and report on the integrity of these new signatures before they are installed.
  • Filter/Exclusion: Exclude events where the parent process is ccmexec.exe (SCCM) or wuauclt.exe (Windows Update) occurring between 01:00 and 05:00 UTC. Additionally, filter for specific file hashes of known Microsoft-signed update packages.

• Scenario: Deployment of Software Updates via Ansible Automation

  • Context: The DevOps team runs an Ansible playbook to patch critical security software across the server fleet. This automation invokes ShimRatReporter as part of a post-installation verification step to ensure the new shim layers are correctly registered in the Windows Registry.
  • Filter/Exclusion: Create an exclusion for events originating from specific service accounts (e.g., svc_ansible_deploy) or where the command line arguments contain keywords like -playbook, -patch, or specific Ansible inventory hostnames.

• Scenario: User-Initiated Security Scans via CrowdStrike Falcon

  • Context: A security administrator manually triggers an on-demand scan using the CrowdStrike Falcon console. The ShimRatReporter process is spawned to analyze potential conflicts between the new scan engine and existing system shims, generating a detailed report for the admin dashboard.
  • Filter/Exclusion: Filter out events where the initiating user belongs