ThreatFox: Unknown Stealer IOCs

Hunt Hypothesis

The ThreatFox: Unknown Stealer IOCs rule detects potential reconnaissance and data exfiltration activities associated with a previously unknown stealer malware, leveraging suspicious network connections and file artifacts. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate early-stage compromise by an advanced threat actor targeting sensitive data.

IOC Summary

Malware Family: Unknown Stealer Total IOCs: 11 IOC Types: url, domain

KQL: Domain Hunt

// Hunt for DNS queries to known malicious domains
// Source: ThreatFox - Unknown Stealer
let malicious_domains = dynamic(["purematrixa.com", "wiseview58.com", "anvil-89.com", "iloveblondegirl.top"]);
DnsEvents
| where Name has_any (malicious_domains)
| project TimeGenerated, Computer, Name, IPAddresses, QueryType
| order by TimeGenerated desc

KQL: Url Hunt

// Hunt for access to known malicious URLs
// Source: ThreatFox - Unknown Stealer
let malicious_urls = dynamic(["https://sites.google.com/newappclaude.com/clau-ver-un-30", "https://turbowave45.com/", "https://purematrixa.com/1751517", "https://anvil-89.com/curl/b2ebd894810ccc6df1fccbceeaf09f5c9be6dbf3f8386c915b26e78c28ac3563", "https://sites.google.com/newpayservices.com/cdx-biz-ver-un-v27", "https://wiseview58.com/hjpjsp2/", "https://anvil-89.com/curl/db7bd4c559aa3fb93d63739f16264aae68c911adc95b9f97cc7529c52fd15a87"]);
UrlClickEvents
| where Url has_any (malicious_urls)
| project Timestamp, AccountUpn, Url, ActionType, IsClickedThrough
| order by Timestamp desc

Required Data Sources

References

• ThreatFox — Unknown Stealer

False Positive Guidance

• Scenario: Legitimate System Update via Chocolatey
  Description: A system administrator uses Chocolatey to install a legitimate software update, which includes a script that matches one of the IOCs.
  Filter/Exclusion: process.name != "choco.exe" OR process.parent.name != "choco.exe"

• Scenario: Scheduled Job for Log Rotation
  Description: A scheduled task runs a script to rotate and archive logs, which inadvertently matches an IOC due to similar file names or paths.
  Filter/Exclusion: file.path != "C:\\Windows\\System32\\logrotate.exe" OR process.name != "logrotate.exe"

• Scenario: Admin Task for User Management
  Description: An admin uses PowerShell to manage user accounts, and the script includes a command that matches an IOC due to similar syntax.
  Filter/Exclusion: process.name != "powershell.exe" OR user.name != "Administrator"

• Scenario: Legitimate Third-Party Tool Execution
  Description: A legitimate third-party tool (e.g., 7-Zip, WinRAR) is executed, and one of its components matches an IOC due to shared strings.
  Filter/Exclusion: process.name != "7z.exe" OR process.name != "WinRAR.exe"

• Scenario: Malware Analysis Environment Testing
  Description: A security analyst is testing a benign file in a sandboxed environment, and the file contains strings that match the IOC due to false positives.
  Filter/Exclusion: process.parent.name != "sandbox.exe" OR process.parent.name != "vmtoolsd.exe"