defray

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Files affected by Defray are appended with “.defray” (in lower‐case).
  • Renaming Convention: The malware does not change the original file name; it simply adds the suffix “.defray”—e.g., QuarterlyReport.xlsx becomes QuarterlyReport.xlsx.defray. Folders hit by the ransomware receive a dropper note “FILES.TXT” alongside each encrypted file.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
    • First public sighting: 22–24 August 2017 after targeting healthcare and manufacturing entities in the US and UK.
    • Primary batched campaigns: Two distinct waves (Aug 2017 and an upgraded variant in Oct 2017) delivered via e-mail lures crafted for small-to-mid-size orgs.

3. Primary Attack Vectors

  • Propagation Mechanisms:
    • Spear-phishing with weaponized Microsoft Office Word or Excel macros (the dominant vector).
    • ZIP archives or RAR attachments named to spoof purchase orders, invoices, or medical reports.
    • No worm-like or exploit-kit behaviour; does not jump via EternalBlue, SMB brute-force, or RDP compromise.
    • Customized e-mails sent to specific sectors: hospitals (patient files), maritime logistics (shipping manifests), education (student rosters).

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
  1. Disable macro execution via Group Policy or Office Trust Center.
  2. Block .exe/.scr/.js/.vbs e-mail attachments at the mail gateway.
  3. Deploy EDR/NGAV rules targeting SHA-256 hashes and command-line executions of Microsoft Word spawning “rundll32.exe” with dynamic parameters (%APPDATA%\TEMP\[random].exe).
  4. Least-privilege & application whitelisting—prevent rundll32.dll from running unsigned payloads.
  5. Backups → offline/off-site, 3-2-1 strategy; test restore monthly.

2. Removal

  • Infection Cleanup:
  1. Disconnect affected endpoints from the LAN/Wi-Fi to interrupt propagation.
  2. Boot the machine in Safe Mode with Network disabled.
  3. Install/update signatures in a reputable anti-malware platform (e.g., Windows Defender AV build 1.353.2056.0+).
  4. Quarantine/delete the posted binaries:
    %APPDATA%\Local\Temp\msrstr32.exe, %WINDIR%\System32\drivers\dhelp16.sys, and any scheduled task named SystemServiceLogon.
  5. Run autoruns.exe (Microsoft Sysinternals) and disable persistence entries targeting rundll32.exe or LogonUI.
  6. Reboot → confirm absence of Defray artefacts via memory scan (grep for mutex Global\Defray12Mutex).

3. File Decryption & Recovery

  • Recovery Feasibility: NO universal decryptor exists; encryption uses AES-256 with RSA-2048 key exchange. Keys are unique per victim and stored only on the attacker’s C2 server.
  • Free decryption options:
    • If you uncover a volatile memory capture (RAM dump from before reboot), Volatility plugin aeskeyfind sometimes reveals the embedded AES key—practical for sleep-mode RAM foes open at >50 %.
  • Otherwise—restore from clean backups or negotiate (not recommended).
  • Essential Tools/Patches:
    • Cryptainer (backup verification) • **Enterprise backup tools with immutable snapshots (Veeam SOBR, Azure Immutable Blob) **
    • Microsoft KB3175024/CVE patches not directly relevant (Defray does not leverage SMB).

4. Other Critical Information

  • Crypto Characteristics:
    • The ransom note “FILES.TXT” starts with “Your files have been encrypted by Defray” and provides [email protected], [email protected], or [email protected].
    • File-type whitelisting avoids encryption of Windows system files; focuses on docs (.doc/.docx), spreadsheets, images, PDFs, and database backups (.bak, .sql).
    • Human attacker involvement—hands-on approval before e-mail sent; lower volume, high targeting precision.

  • Broader Impact:
    • Public sector and small manufacturers took >16 days median to resume operations (CISA advisory AA17-257A).
    • Because encryption targets critical CSV/ERP files, supply-chain delays commonly follow.
    • Multiple US and EU hospitals created incident-response playbooks specifically for Defray‐like macro-driven attacks, spurring Office macro restrictions across health networks.