This detection identifies the presence of the PELockNTv203 malware variant using a specific YARA signature to uncover potential fileless or memory-resident threats within the Azure Sentinel environment. Proactive hunting for this indicator is essential to validate its low-severity classification and prevent lateral movement before it escalates into a more critical incident.
rule PELockNTv203
{
meta:
author="malware-lu"
strings:
$a0 = { EB 02 C7 85 1E EB 03 CD 20 C7 9C EB 02 69 B1 60 EB 02 EB 01 }
condition:
$a0 at pe.entry_point
}This YARA rule can be deployed in the following contexts:
This rule contains 1 string patterns in its detection logic.
Here are 5 specific false positive scenarios for the PELockNTv203 detection rule, along with targeted filters and exclusions:
Scenario: Microsoft Defender Antivirus Real-Time Protection Scanning
MsMpEng.exe process frequently locks Portable Executable (PE) files during real-time scanning or on-access updates to prevent modification while integrity checks are performed. This often triggers the rule when users open documents or install patches.MsMpEng.exe from the detection logic, specifically targeting file paths within %ProgramFiles%\Windows Defender\. Alternatively, add a filter to ignore events where the ProcessName matches MsMpEng.exe and the action is “File Lock” on .dll, .exe, or .docx extensions.Scenario: Scheduled System Backup via Veeam Agent
VeeamAgentService) locks PE files (including system binaries and user documents) to create consistent snapshots before backup operations commence. This is a legitimate administrative task that mimics malicious locking behavior.veeamagent.exe. Ensure the filter specifically targets file locks on the C:\ drive root and user profile directories.Scenario: Group Policy Object (GPO) Application by Sysmon
gpupdate.exe or gpsvc) may lock configuration files and policy templates stored as PE artifacts to apply changes. This often happens during user logon