Cerber3

Hunt Hypothesis

This detection rule identifies potential reconnaissance or lateral movement activities where adversaries attempt to establish persistent access points within the Azure environment. Proactively hunting for this behavior is essential because early identification of these low-severity signals allows the SOC team to correlate them with broader attack chains before they escalate into critical incidents.

YARA Rule

rule cerber3{
meta:
  author = "pekeinfo"
  date = "2016-09-09"
  description = "Cerber3 "
strings:
  $a = {00 6A 00 68 80 00 00 00 6A 03 6A 00 6A 03 6A  01 8B 85}
  $b = {68 3B DB 00 00 ?? ?? ?? ?? 00 ?? FF 15}
  
condition:
  1 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 2 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 4 specific false positive scenarios for the Cerber3 detection rule in an enterprise environment, including suggested filters and exclusions:

• Automated Patch Management Deployments

  • Scenario: The Windows Update Agent or third-party tools like WSUS (Windows Server Update Services) and SCCM (System Center Configuration Manager) trigger the rule when they execute background installation scripts. These processes often spawn temporary elevated sessions to apply security patches, mimicking suspicious user activity patterns that Cerber3 flags as anomalous behavior.
  • Suggested Filter/Exclusion: Create an exclusion for process paths containing C:\Windows\SoftwareDistribution and C:\Program Files (x86)\Microsoft Intune. Additionally, filter out events occurring during the defined maintenance window (e.g., 02:00–04:00 UTC) where the source IP belongs to the internal patch management subnet.

• Scheduled Backup and Data Archiving Jobs

  • Scenario: Enterprise backup solutions such as Veeam Backup & Replication, Commvault, or Azure Backup Agent run scheduled jobs that involve high-volume file I/O and temporary privilege escalation to access shared drives (SMB) and SQL databases. The Cerber3 rule may interpret the rapid succession of file creation, modification, and network connection attempts by these service accounts as a potential data exfiltration attempt.
  • Suggested Filter/Exclusion: Exclude specific Service Accounts used for backups (e.g., svc_backup_prod, azurbackup-agent) from the rule logic. Furthermore, add a filter to ignore events where the source process name matches known backup executables like Veeam.Backup.Service.exe or CommServe.exe.

• Identity and Access Management (IAM) Provisioning Tasks

  • Scenario: Automated identity synchronization tools like **Microsoft