Network Win7x86

Hunt Hypothesis

The hypothesis is that the detection rule identifies potential adversary activity involving network communication from a Windows 7 x86 system, which may indicate the use of legacy infrastructure for persistent or covert operations. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate potential long-term access or data exfiltration from outdated systems.

YARA Rule

rule Network_Win7x86 {
    meta:
        author = "Jaume Martin"
    condition:
        hash.md5(0, filesize) == "548889baed7768b828d9c2f373abd225"
}

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 System Maintenance Task
  Description: A legitimate scheduled task runs a system maintenance script that uses network-related tools (e.g., netstat, ping, or ipconfig) to check network status.
  Filter/Exclusion: process.name != "netstat.exe" AND process.name != "ping.exe" AND process.name != "ipconfig.exe"

• Scenario: Windows Update Installer
  Description: The Windows Update installer (wusa.exe) may perform network operations to download updates.
  Filter/Exclusion: process.name != "wusa.exe"

• Scenario: Admin Performing Network Diagnostics
  Description: An administrator uses tracert or nslookup to troubleshoot network connectivity issues.
  Filter/Exclusion: process.name != "tracert.exe" AND process.name != "nslookup.exe"

• Scenario: Antivirus Scan Using Network Tools
  Description: An antivirus tool (e.g., Windows Defender) may use network-related utilities during a scan.
  Filter/Exclusion: process.name != "WindowsDefender.exe" AND process.name != "microsoft Defender.exe"

• Scenario: Log Collection via PowerShell
  Description: A PowerShell script runs to collect system logs over the network using tools like wevtutil or certutil.
  Filter/Exclusion: process.name != "powershell.exe" OR (process.name == "powershell.exe" AND command_line NOT LIKE "*wevtutil*" AND command_line NOT LIKE "*certutil*")