This YARA rule targets specific memory patterns associated with the MEW10byNorthfox malware family, indicating the presence of a low-severity threat actor attempting to establish a foothold or execute malicious code within the environment. Proactively hunting for this signature in Azure Sentinel allows the SOC team to identify early-stage infections or dormant payloads before they escalate to more impactful post-exploitation activities or lateral movement.
rule MEW10byNorthfox
{
meta:
author="malware-lu"
strings:
$a0 = { 33 C0 E9 [2] FF FF ?? 1C [2] 40 }
condition:
$a0
}This YARA rule can be deployed in the following contexts:
This rule contains 1 string patterns in its detection logic.
Scenario: A developer or DevOps engineer uses a legitimate YARA scanning tool (such as yara CLI, Yara-Native, or integration with VirusTotal Enterprise) to scan a large directory of application binaries or container images for known malware signatures. The rule MEW10byNorthfox is part of the Northfox YARA rule set, which is often deployed in CI/CD pipelines or endpoint scanning agents.
yara.exe, yara64.exe) and the parent process is a build agent (e.g., jenkins.exe, azure-devops-agent.exe, github-runner.exe) or a container runtime (docker.exe, containerd.exe).Scenario: An endpoint detection and response (EDR) agent (e.g., CrowdStrike Falcon, Microsoft Defender for Endpoint, or Carbon Black) performs a full or incremental scan of the file system. These agents often use YARA rules internally or via user-defined rule packs to identify suspicious files. The rule MEW10byNorthfox may be loaded into the EDR’s YARA engine.
FalconSensor.exe, MsMpEng.exe, CbService.exe) and the operation is a file read or scan (Read, Scan) rather than a write or execute.Scenario: A security team or incident responder manually runs a YARA scan on a specific folder or file to triage a suspected compromise. They use a standalone YARA tool or a script that invokes the YARA engine to check for the MEW10byNorthfox signature.