Auto-generated rule - file 9acba7e5f972cdd722541a23ff314ea81ac35d5c0c758eb708fb6e2cc4f598a0

Hunt Hypothesis

The rule detects potential adversary behavior involving unauthorized file access or modification in the Azure environment, which could indicate lateral movement or data exfiltration. SOC teams should proactively hunt for this behavior to identify and mitigate early-stage threats that may evade traditional detection methods.

YARA Rule

rule GRIZZLY_STEPPE_Malware_2
{

   meta:
      description = "Auto-generated rule - file 9acba7e5f972cdd722541a23ff314ea81ac35d5c0c758eb708fb6e2cc4f598a0"
      author = "Florian Roth"
      reference = "https://goo.gl/WVflzO"
      date = "2016-12-29"
      hash1 = "9acba7e5f972cdd722541a23ff314ea81ac35d5c0c758eb708fb6e2cc4f598a0"
      hash2 = "55058d3427ce932d8efcbe54dccf97c9a8d1e85c767814e34f4b2b6a6b305641"
      
   strings:
      $x1 = "GoogleCrashReport.dll" fullword ascii
      $s1 = "CrashErrors" fullword ascii
      $s2 = "CrashSend" fullword ascii
      $s3 = "CrashAddData" fullword ascii
      $s4 = "CrashCleanup" fullword ascii
      $s5 = "CrashInit" fullword ascii

   condition:
      ( uint16(0) == 0x5a4d and filesize < 1000KB and $x1 ) or ( 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 6 string patterns in its detection logic.

References

False Positive Guidance

Scenario: Scheduled System Maintenance Task
Description: A legitimate scheduled task (e.g., Task Scheduler or cron job) is running a script that generates a high volume of file activity.
Filter/Exclusion: process.parent_process_name:"Task Scheduler" or process.parent_process_name:"cron"
Scenario: Antivirus or Endpoint Protection Scan
Description: A security tool like Windows Defender, Kaspersky, or Bitdefender is performing a full system scan, which may trigger file access alerts.
Filter/Exclusion: process.name:"Windows Defender Antivirus" or process.name:"kavsvc.exe"
Scenario: Log File Rotation or Archive Process
Description: A system or application (e.g., Logrotate, rsyslog, or Logstash) is rotating or archiving log files, which can cause frequent file modifications.
Filter/Exclusion: file.name:"*.log" or process.name:"logrotate"
Scenario: Database Backup Job
Description: A database backup process (e.g., **MySQL, **PostgreSQL, or **SQL Server) is running and accessing multiple files. *Filter/Exclusion:* process.name:“mysqldump”orprocess.name:“pg_dump”`
Scenario: User-Initiated File Copy or Move Operation
Description: A user is manually copying or moving files using tools like Robocopy, rsync, or cp.
Filter/Exclusion: process.name:"robocopy.exe" or process.name:"rsync"