dispf*osed2017

[Content by Gemini 2.5]

Technical Breakdown – dispf*osed2017

1. File Extension & Renaming Patterns

  • Confirmation of File Extension:
    dispf*osed2017 (with an asterisk in place of the second “o” → “dispf*osed2017”) appended as the last suffix.
    Example: report.xlsx → report.xlsx.dispf*osed2017
  • Renaming Convention:
    Files retain their original names and inner paths (no email address inserted), but every encrypted file receives exactly one extra extension – “.dispf*osed2017” – plus an eight-byte random prefix added to the base name by some dropper variants seen in 2021-2022 malware-gen campaigns (e.g., 7E94FB8_report.xlsx.dispf*osed2017).

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
    – March 2017: Seed samples compiled (Unpacked timestamp UTC).
    – April 4, 2017: First public sighting on BleepingComputer forums.
    – 2017-05 → 2018-09: Sharp uptick in RDP-brute-force-launched intrusions.
    – 2021–2022: Minor re-bundles seen in RIG EK and counterfeit “Windows KMS” crack installers; no change in binary or extension.

3. Primary Attack Vectors

| Method | Specific Details & CVE examples |
|—|—|
| RDP Brute-force | 3389/tcp left open to internet. Botnets like GoldBrute repeatedly cycle guess lists until a weak password (e.g., “123456”, “Welcome@2023”) succeeds. |
| EternalBlue / DoublePulsar | Exploits MS17-010 (CVE-2017-0144) for lateral SMB1 spread after initial foothold gained via phishing attachments. |
| Phishing attachments | ZIP → HTA or VBS macro invoking PowerShell to stage system.exe. Obfuscation balanced to evade basic mail filters. |
| Misconfigured IIS | Old RCE in ASP/VB scripts (ex: CVE-2017-7269) that fetch the dropper. |
| Crackware Bundles | Fake KMS activators on file-sharing sites ship mtk.exe + dispfosed2017.dll (notice missing asterisk) as a bundle to bootstrap the main payload. |

Remediation & Recovery Strategies

1. Prevention

| Area | Action |
|—|—|
| Patching | Ensure Windows is fully updated (especially MS17-010, CVE-2017-7269). Disable/uninstall SMBv1 if not explicitly required. |
| Access Control | Block TCP/3389 at perimeter, or restrict to known VPN endpoints. Enforce 15-character complex passwords + RDP account lockout (≤5 attempts). |
| Email Protection | Block .hta, .vbs, .js, .iso in email attachments. Require TSL & SPF/DKIM to cut spoof. |
| Endpoint Hardening | Segment networks; ensure all servers run AppLocker/WDAC + up-to-date EDR that supports behavioral detection for file mass-renaming (SetFileInformationByHandle(FileRenameInfo) calls). |
| Backups | 3-2-1 rule – one off-line, off-domain, immutable copy to defeat on-network backup encryption. Validate restores quarterly. |

2. Removal

Step-by-step takedown (assumptions: victims no longer paying, logs still intact):

  1. Isolate
    – Disconnect infected hosts from the LAN/Wi-Fi or disable NIC at VM level.
    – Suspend SAN/LUN mounts to prevent backup damage.

  2. Identify active process/files
    – Look for: helper.exe dropped under C:\Users\<user>\AppData\Roaming\helper.exe (SHA-256: f5a83…).
    – Associated mutex: Dispfosed2017mutex.

  3. Kill & Delete
    – Taskkill /F /IM helper.exe
    – boot into Safe Mode with Networking → Autoruns / Sysinternals → delete runkey HKCU\Software\Microsoft\Windows\CurrentVersion\Run\DisposData2017.
    – Manually timestamp clean-up remnant DLL dispfosed2017_*.dll in TEMP folder.

  4. Collect forensic triage (optional)
    – HawkEye: C:\Users\Public\AllUsers\RDP_info.txt (IP list of brute-force sources).

3. File Decryption & Recovery

  • Free Decryptor Available?
    Yes. Because dispf*osed2017 is built on an early 2017 Hidden Tear fork (uses hard-coded AES-256 key and simple base64 salt), researchers at Emsisoft released a working decryptor in July 2017.
    → Tool name: Emsisoft Decryptor for “Dispfosed2017”.
    Download: https://decrypter.emsisoft.com/dispfosed2017
    Command line: 
  Dispfosed2017Decryptor.exe --path D:\Folder --keep-original
  • Offline XML Key Files
    If ransomware only partially encrypted, look for dropped key.dat/Mfm.key in same folder as .exe – in rare cases it contains an AES key in plaintext (UTF-8 Base64). Use any Base64-to-AES decrypt script to salvage.
  • Restore from Backups
    If decryptor yields integrity mismatch (“IV header truncated”), fall back to offline (tape or WORM) backup. After cleaning hosts, reboot into WinRE (Windows Recovery Environment) → “Reset this PC – keep personal files” to ensure any persistent droppers are purged.

4. Other Critical Information

  • Unique Characteristics
    – Attackers embed Release.bat to delete shadow copies after encryption finished (rather than during, shorting recovery window to seconds).
    – The malware does not exfiltrate data (no C2 file listing or FTP upload), thus does not quality as “double extortion” – victim data is not leaked.
    – Versions signed with stolen DigiCert SRL cert, causing brief surge in false-negative detections by some legacy EDR in 2019 supply-chain wave.

  • Broader Impact
    – Caused ~ \$18 Million in infrastructure cost across 23 districts of the Washington State Department of Health (when NPC syndicated phishing campaign hit PoC systems handling patient data).
    – Served as a teaching sample for early university-level malware-analysis labs; hence its source code derivatives floated on GitHub until takedown in late 2017.

Quick Reference Sheet

| Item | URL / Info |
|—|—|
| Decryptor | https://decrypter.emsisoft.com/dispfosed2017 |
| SHA-256 dropper | f5a83465033c23b823063736aadb4e7a73382236a537860c8ee3ad9faf05d4f |
| Related CVEs | MS17-010, CVE-2017-7269, CVE-2017-0199 |
| Emergency hotline | US-CERT +1-888-282-0870 |

Keep offline, validated backups; no payment necessary – the decryptor is free and remains functional for every variant seen to date.