ThreatFox: Aisuru IOCs

Hunt Hypothesis

This hunt detects adversary activity involving specific Indicators of Compromise (IOCs) linked to the Aisuru threat actor, which may signal early-stage reconnaissance or lateral movement within the environment. Proactively hunting for these IOCs in Azure Sentinel is critical because their high severity rating suggests a potential immediate risk that requires rapid containment before adversaries can establish persistence or exfiltrate sensitive data.

IOC Summary

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

KQL: Ip Hunt

// Hunt for network connections to known malicious IPs
// Source: ThreatFox - Aisuru
let malicious_ips = dynamic(["43.134.49.218", "43.128.113.133"]);
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(["43.134.49.218", "43.128.113.133"]);
DeviceNetworkEvents
| where RemoteIP in (malicious_ips)
| project Timestamp, DeviceName, RemoteIP, RemotePort, InitiatingProcessFileName, ActionType
| order by Timestamp desc

Required Data Sources

References

• ThreatFox — Aisuru

False Positive Guidance

Here are 4 specific false positive scenarios for the ThreatFox: Aisuru IOCs detection rule, including targeted filters and exclusions suitable for an enterprise environment:

• Scenario: Antivirus Engine Updates via Scheduled Task

  • Context: Enterprise endpoints running CrowdStrike Falcon or Microsoft Defender often trigger background processes that query external threat intelligence feeds. If the Aisuru IOCs include specific update servers or hash signatures used by these vendors, the scheduled nightly update job (e.g., Task Scheduler: CrowdStrike_Update) will generate a match.
  • Filter/Exclusion: Create an exclusion rule based on the Process Name (FalconService.exe or MsMpEng.exe) and Parent Process (svchost.exe). Additionally, exclude traffic originating from the specific update server IP ranges defined in the vendor’s documentation during maintenance windows (e.g., 02:00–04:00 AM local time).

• Scenario: Security Information and Event Management (SIEM) Data Ingestion

  • Context: The organization utilizes a SIEM platform like Splunk Enterprise Security or IBM QRadar. These systems frequently ingest logs from external threat intelligence platforms. If the Aisuru IOCs correspond to the API endpoints used by the SIEM’s connector service, the ingestion process will trigger alerts on the management server itself rather than on user workstations.
  • Filter/Exclusion: Exclude all events where the Source Host belongs to the SIEM-Management subnet (e.g., 10.20.50.0/24). Alternatively, filter by Process Path, ensuring exclusions apply only if the executable path contains \Program Files\Splunk\bin\ or \IBM\QRadar\.

• **Scenario: Third-Party EDR