ThreatFox: VShell IOCs

Hunt Hypothesis

This hunt targets adversary behavior involving the execution of VShell-related indicators of compromise to identify potential command-and-control communications or unauthorized remote access sessions. Proactively hunting for these specific IOCs in Azure Sentinel is critical because early detection of VShell activity can reveal stealthy lateral movement and prevent data exfiltration before broader network anomalies occur.

IOC Summary

Malware Family: VShell Total IOCs: 2 IOC Types: ip:port

KQL: Ip Hunt

// Hunt for network connections to known malicious IPs
// Source: ThreatFox - VShell
let malicious_ips = dynamic(["82.156.155.15", "151.243.137.78"]);
CommonSecurityLog
| where DestinationIP in (malicious_ips) or SourceIP in (malicious_ips)
| project TimeGenerated, SourceIP, DestinationIP, DestinationPort, DeviceAction, Activity
| order by TimeGenerated desc

KQL: Ip Hunt Device

// Hunt in Defender for Endpoint network events
let malicious_ips = dynamic(["82.156.155.15", "151.243.137.78"]);
DeviceNetworkEvents
| where RemoteIP in (malicious_ips)
| project Timestamp, DeviceName, RemoteIP, RemotePort, InitiatingProcessFileName, ActionType
| order by Timestamp desc

Required Data Sources

References

• ThreatFox — VShell

False Positive Guidance

Here are specific false positive scenarios for the ThreatFox: VShell IOCs detection rule in an enterprise environment, along with suggested filters and exclusions:

• Endpoint Management Agent Updates

  • Scenario: The organization’s Endpoint Detection and Response (EDR) or Mobile Device Management (MDM) solution (e.g., CrowdStrike Falcon, Microsoft Intune, or Trend Micro) pushes a security definition update that includes the VShell certificate chain or specific IOCs as part of its “Safe List” database. This triggers the rule when agents on thousands of workstations simultaneously validate these new signatures during their scheduled morning sync window.
  • Filter/Exclusion: Create an exclusion for process paths associated with known management tools (e.g., C:\Program Files\CrowdStrike\csagent.exe or C:\Windows\System32\svchost.exe running under the LocalService account) communicating with internal update servers. Additionally, exclude traffic originating from the specific IP ranges of the EDR/MDM management consoles.

• Automated Vulnerability Scanning Jobs

  • Scenario: A scheduled vulnerability assessment job (e.g., using Tenable Nessus, Qualys, or Rapid7 InsightVM) runs nightly against the internal network. The scanner actively probes web servers and application gateways, specifically checking for known VShell configurations to verify compliance with security baselines. This generates legitimate hits on the VShell IOCs during the scan window (e.g., 02:00 – 04:00 UTC) across all scanned subnets.
  • Filter/Exclusion: Exclude alerts where the source IP belongs to the vulnerability scanner’s management cluster and the destination port is restricted to standard scanning ports (80, 443, 8443). Implement a time-based filter