ThreatFox: ValleyRAT IOCs

Hunt Hypothesis

This hunt targets adversary behavior involving the execution of ValleyRAT remote access trojan components by monitoring network and process activity against specific Indicators of Compromise (IOCs). Proactively hunting for these signatures in Azure Sentinel is critical to identify early-stage lateral movement or data exfiltration attempts before they escalate into full-blown incidents.

IOC Summary

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

KQL: Ip Hunt

// Hunt for network connections to known malicious IPs
// Source: ThreatFox - ValleyRAT
let malicious_ips = dynamic(["137.220.140.4"]);
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(["137.220.140.4"]);
DeviceNetworkEvents
| where RemoteIP in (malicious_ips)
| project Timestamp, DeviceName, RemoteIP, RemotePort, InitiatingProcessFileName, ActionType
| order by Timestamp desc

Required Data Sources

References

• ThreatFox — ValleyRAT

False Positive Guidance

Here are specific false positive scenarios for the ThreatFox: ValleyRAT IOCs detection rule, tailored for an enterprise environment:

• Software Deployment via SCCM/Intune: The deployment of a new third-party remote support agent (e.g., LogMeIn Rescue or TeamViewer) by the IT Operations team often triggers this rule. These agents share similar network behaviors and file hashes with ValleyRAT components, particularly during the initial installation or service registration phase where they establish outbound connections to their management servers.

  • Suggested Filter: Exclude traffic originating from specific SCCM/Intune deployment servers (e.g., Deploy-SRV-01, SCCM-DP-Cluster) and restrict alerts to only occur outside of the standard maintenance window (e.g., 02:00–04:00 UTC) if the installation is not scheduled during that time.

• Scheduled Antivirus Definition Updates: Enterprise endpoint protection suites like CrowdStrike Falcon or Microsoft Defender for Endpoint frequently update their heuristic engines and threat intelligence feeds. During these updates, the AV service may download and stage a component that matches a ValleyRAT hash or network signature before the full scan completes, mimicking the behavior of the RAT’s initial handshake.

  • Suggested Filter: Create an exclusion based on the process name MsMpEng.exe (Defender) or CfSvc.exe (CrowdStrike) when communicating with known vendor update endpoints (e.g., *.update.microsoft.com, *.crowdstrike.com) and exclude events where the file integrity hash matches a known “Good” baseline from the previous 30 days.

• IT Helpdesk Remote Troubleshooting Sessions: When Tier 2 or Tier 3 support engineers initiate remote sessions to troubleshoot user workstations, they often utilize internal tools that inject scripts or temporary agents into the target machine. If the helpdesk