etols

[Content by Gemini 2.5]

Community Threat Dossier – “ETOLS” Ransomware

(File extension: .etols)

TECHNICAL BREAKDOWN

1. File Extension & Renaming Patterns

  • Exact marker: .etols is appended as a second extension (e.g., Quarterly_Report.xlsx.etols).
  • Typical convention:
    OriginalName . [original-extension] . etols – the malware does not wipe the original name or extension; it simply tacks “.etols” to the end, making quick visual triage easy.
  • Dropped marker file: “_readme.txt” is created in every folder where encryption occurs.

2. Detection & Outbreak Timeline

  • Initial sightings: Late-October 2022 (earliest uploads to ID-Ransomware & VirusTotal: 29 Oct 2022).
  • Peak distribution waves: Nov-2022 through Q1-2023; still circulating mid-2024 as affiliates rotate payloads.
  • Note: ETOLS is simply a new “brand” of the STOP/Djvu franchise; decryption research therefore tracks the parent family, not this exact suffix.

3. Primary Attack Vectors

STOP/Djvu – and by extension ETOLS – relies overwhelmingly on two infection paths:

a. Pirated-software bundles
– Fake Photoshop, Windows activators (KMS), game cracks, keygens delivered via torrent & one-click-hosting sites.
– The installer drops either a .NET loader or a heavily obfuscated NSIS package that downloads the final ETOLS DLL.

b. SmokeLoader back-chain
– Malvertising on YouTube “how-to” videos (especially for pirated software) pushes SmokeLoader, which in turn pulls down the same ETOLS DLL.

Historical vectors that occasionally reappear
– Rig Exploit Kit (IE-based), although this is now marginal.
– NO evidence of network worming (EternalBlue/SMB) – ETOLS is purely user-invoked or dropped by SmokeLoader.

REMEDIATION & RECOVERY STRATEGIES

1. Prevention (STOP/Djvu specific)

  • ❌ Never mount pirated/cracked installers. >90 % of ETOLS infections start this way.
  • Browser ad-blockers plus DNS filtering (Quad9, Cloudflare 1.1.1.2) remove most SmokeLoader gate domains.
  • Application whitelisting (Windows Defender Application Control / AppLocker) blocks execution of unsigned %TEMP%\*.exe & %APPDATA%\*.dll – the two directories STOP uses.
  • Patch Microsoft Office & browsers (old EK vectors) but, more important, disable Office macros company-wide.
  • Lateral movement is rare; still, disable RDP if unused and segment VIP data shares to limit blast radius.

2. Removal Step-by-Step

  1. Physically isolate the machine (pull Ethernet / disable Wi-Fi).
  2. Collect a triage image if legal/forensic needs exist (Volatility memory dump first; then disk image via FTK Imager).
  3. Copy the ransom note (_readme.txt) – it contains the malware version & affiliate ID, useful for decryption checks.
  4. Boot into Safe Mode with Networking. Run:
    – Malwarebytes 4.x (full scan)
    – ESET STOPDecrypterRemover (removes persistence registry keys).
  5. During scan you will normally see:
    – C:\Users\<user>\AppData\Local\<random>\ican328.dll ← main payload
    – Scheduled task “Time Trigger Task” or “WindowsUpdatesCheck” ← autostart
  6. Let the AV delete items; reboot normally; verify scheduled tasks & startup folders are clean; confirm network is silent (no new etols files after 5 min).

3. File Decryption & Recovery

  • NEWS YOU CAN USE:
    – If ETOLS encrypted your files with an OFFLINE key, Michael Gillespie & Emsisoft provide a free decryptor.
    – If the key is ONLINE (malware talked to its command server), no free decryption exists at the time of writing.

How to tell the difference

  1. Open any _readme.txt; towards the bottom you will see “Your personal ID:”.
  2. If the last character of that 40-char string is ‘t1’ (or you find ‘offline@kfast’ email), you are likely offline.
  3. Download the latest Emsisoft STOPDecrypter (v1.0.0.6 or newer). Point it at a PAIR of identical files—one original, one .etols (e.g., from backup or email attachment).
  4. Tool will:
    – derive the offline key → decrypt all files on that machine if key matches;
    – or tell you “unable to brute-force – online key”.

No backup + online key?

  • File repair: only certain file types have partial recovery (see below).
  • Otherwise your choices = pay (discouraged) or rebuild from backup/off-site snapshots.

4. Additional Critical Information

  • Partial file recovery: STOP/Djvu only encrypts the first 5 MB of each file. For MP3/MP4/JPG you can often carve playable media with tools like:
    – MP3val, Video Repair Tool (Grau), or photorec (but rename .etols back to original ext first).
  • No data exfiltration – purely destructive; therefore no leak blog.
  • Affiliate rotation – new extension every 1–2 weeks (同一payload, 新皮肤). Expect cousins: .lisp, .foop, .nury, .thxl, etc. All handled by the same decryptor.
  • Ransom amount: static USD 490 if contacted within 72 h; doubles to 980 USD after; attackers use [email protected] / [email protected] plus Bitmessage ID.
  • Wider impact: Because it piggybacks on piracy culture, home users & SOHO are hit hardest; >680 k confirmed submissions to ID-Ransomware, making STOP/Djvu the #1 reported family since 2019.

Community rule of thumb:
In ETOLS infections, OFFLINE = recoverable, PIRACY = patient-zero.
Cut the piracy habit, back up nightly, and you’ll outrun this family every time.