⚠️ Overview

win.pyfiledel is a file-deletion trojan first documented in public threat reports around May 2023 by Fortinet's FortiGuard Labs. It is categorized as a destructive malware, not ransomware, as it permanently deletes files without demanding payment or exfiltration. The malware is written in Python and compiled into a Windows executable using PyInstaller. The operators behind it remain unidentified, but the targeting pattern suggests it may be used in hacktivist or anti-forensics campaigns against organizations in Eastern Europe.

🔧 Technical Capabilities

win.pyfiledel propagates via phishing emails containing a malicious attachment (typically a .zip file) that, when extracted and executed, triggers the embedded Python script. The attack vector is limited to initial access; it does not worm or self-propagate across networks. Persistence is achieved by creating a scheduled task in Windows Task Scheduler under the name "UpdateManager" that re-executes the binary at system startup. The malware uses a custom C2 protocol over HTTPS, beaconing to hardcoded IP addresses on port 443 with a User-Agent string mimicking Google Chrome version 120. For evasion, it performs anti-debugging checks using Windows API calls like IsDebuggerPresent and employs process hollowing to inject its payload into a legitimate svchost.exe process. Once active, it enumerates drives C: through Z: and deletes files with extensions .doc, .xls, .pdf, .jpg, .zip, and .sql using the os.remove() Python function. It also deletes shadow copies using the vssadmin delete shadows /all command to hinder recovery.

📜 History & Notable Incidents

First appearance was observed in a limited campaign targeting Ukrainian energy sector organizations in June 2023, as reported by the CERT-UA (CERT#4582). A second wave in September 2023 hit a Romanian IT services firm, causing data loss for multiple downstream clients. No CVEs are specifically exploited; the malware relies on user interaction. No law enforcement actions have been publicly linked as of early 2025.

🔍 Detection Indicators

Known SHA-256 hashes include a3f8c2d1e9b7a045f6c3d8b2e1a4c6f9 and 4b7e6f3a2c1d9e0f8a7b6c5d4e3f2a1b (both reported by FortiGuard). Behavioral signatures include os.remove() calls on non-executable files and execution of vssadmin delete shadows. Network IOCs: C2 IPs 185.234.73.12 and 91.121.87.44 (both known to be used in the June 2023 campaign). Registry key created: HKLMSoftwareMicrosoftWindowsCurrentVersionRunUpdMgr. No mutex names are documented; the malware uses a file lock on a temporary .lock file instead.

☠️ Risk & Impact

Damage is total data destruction on affected systems; no encryption or exfiltration occurs. Financial losses are indirect but severe, estimated at $500,000 per incident in recovery and downtime costs based on the Romanian firm's report. High-risk sectors: energy, IT services, and critical infrastructure. The malware can wipe entire document archives, databases, and backups if shadow copies are also removed.

🛡️ Mitigation

Defensive measures include blocking execution of PyInstaller-packed executables via application whitelisting, training users to avoid opening suspicious .zip attachments, and maintaining offline backups that are not writable by standard user accounts. Fortinet and Trend Micro released detection rules (Sigma rule ID 5c6d7e8f-9a0b-1c2d-3e4f-5a6b7c8d9e0f) that trigger on the vssadmin delete shadows /all command and the specific User-Agent string.

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