Insta11

Hunt Hypothesis

The Insta11 rule detects potential adversary behavior involving rapid, suspicious file creation or modification patterns that may indicate automated or scripted activity. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate early-stage threats that could escalate into more severe attacks.

YARA Rule

rule Insta11 : Family
{
    meta:
        description = "Insta11"
        author = "Seth Hardy"
        last_modified = "2014-06-23"
        
    condition:
        Insta11Code or Insta11Strings
}

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
• Source Rule

False Positive Guidance

• Scenario: Scheduled Backup Job Using Veeam Backup & Replication
  Filter/Exclusion: process.name != "vbm.exe" or process.name != "vbackup.exe"

• Scenario: System Update via Microsoft Endpoint Manager (Intune)
  Filter/Exclusion: process.name != "setup.exe" or process.name != "msiexec.exe" with parent_process.name == "taskeng.exe"

• Scenario: Database Maintenance Task via SQL Server Agent
  Filter/Exclusion: process.name != "sqlservr.exe" or process.name != "sqlagent.exe" with process.args contains "maintenance"

• Scenario: Log Collection via Splunk Forwarder
  Filter/Exclusion: process.name != "splunkforwarder.exe" or process.args contains "--noauth"

• Scenario: User-Initiated File Transfer via FileZilla
  Filter/Exclusion: process.name != "filezilla.exe" or process.args contains "--passive"