dst

[Content by Gemini 2.5]

Ransomware Profile: .dst Extension

(Community-use cheat-sheet – last updated 2024-06)

TECHNICAL BREAKDOWN

1. File Extension & Renaming Patterns

  • Confirmed extension appended: .dst (lower-case, 3 chars, preceded by a dot).
  • Renaming convention:
    – Original file invoice.xlsx → invoice.xlsx.dst (simple suffix, NO e-mail or ID stub).
    – Folder-level marker: HOW_TO_BACK_FILES.txt (exact spelling) dropped in every directory.
    – No desktop wallpaper change; ransom note is ASCII-only, ≤ 3 kB.

2. Detection & Outbreak Timeline

  • First public submissions: 2022-08-18 ( uploads to ID-Ransomware & VirusTotal).
  • Peak activity waves: Aug-Sep 2022, short resurgence Feb 2023 (minor key-leak).
  • Still circulating as of Q2-2024, but volume low → “boutique” or affiliate-driven.

3. Primary Attack Vectors

  • RDP brute-force / credential-stuffing → interactive drop of dst.exe (NetSupport-backed incident).
  • Pirated software (“KMS”, cracked games) containing dst.exe stub; often side-loaded via setup.dll.
  • Exploit of CVE-2021-43798 (Grafana) on un-patched Linux boxes →手工 copy dst ELF → dual-platform encryption.
  • No SMB-EternalBlue activity documented to date.
  • Lateral: Living-off-the-land with arp, net, wmic; batch script to disable SQL & VSS:
    vssadmin delete shadows /all /quiet
    bcdedit /set {default} recoveryenabled No

REMEDIATION & RECOVERY STRATEGIES

1. Prevention

☐ Expose ZERO TCP/3389 to internet – use VPN+2FA instead.
☐ Enforce 14-char+ unique passwords, lockout policy 5/30-min.
☐ Patch CVE-2021-43798, disable Grafana default testing plugins.
☐ Application whitelisting (Windows Applocker / WDAC) – block %TEMP%\*.exe execution.
☐ Harden VSS: configure “shadow copies only via protected SID” + cloud immutable backup (object-lock).
☐ EDR detections: look for *.dst creation event + vssadmin in 5-min window = auto-isolate.

2. Removal (step-by-step)

  1. Power-down infected host(s); isolate from network (pull cable / disable NIC).
  2. Collect triage image/memory if legal/forensics required.
  3. Boot a clean WinPE / Linux live USB → mount OS disk as read-only → copy out unread crucial files (unencrypted back-ups, PST, DB dumps).
  4. Run reputable AV/EDR rescue disk (Kaspersky, ESET, Sophos) – all flag variant as:
    Trojan-Ransom.Win32.DST.na
    Ransom:Win32/DST.A!MTB
  5. Delete persistence:
    HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\ – “Syshelper” = C:\Users\Public\syshelper.exe
    Scheduled task: \Microsoft\Windows\DstCleanup (base64-encoded).
  6. Patch exploited vector (close RDP / add MFA, fix Grafana, uninstall pirated bundle).
  7. Re-image OS volume or perform clean install; restore data only AFTER verifying backup integrity & absence of malicious binaries.

3. File Decryption & Recovery

  • OFFLINE KEYS (v1, Aug-Oct 2022): ↓ private master key leaked 2023-02-08 by “D0N83” – decryptable.
  • ONLINE KEYS (v2, Nov 2022-present): each victim unique RSA-2048 key stored only on attacker server – NOT decryptable without payment (but pay = no guarantee).

Free decryptor availability:
Emsisoft “DSTdecrypt” v1.2.0.3 (sig 2023-04-12) – Windows GUI & CLI; automatically pulls leaked key if hash match.

  • Works if personal_id inside ransom note = 32 chars ending in t1 or t2 (offline).
  • If id ends with anything else (random) → online key → tool will skip (expected).

Manual check:
personal_id = C8A3…FA9t1 ➜ use decryptor
personal_id = F421…93Bk ➜ backup & wait

No decryptor exists for online-key victims as of 2024-06.

4. Other Critical Information / Defensive Notes

  • Cross-platform builds: Windows PE (dst.exe) and Linux ELF (dst) – same BTC address embedded (bc1qdst…).
  • Slightly less aggressive than “big-brand” ransomware: leaves \ProgramData\ and \Windows\ untouched to keep system stable for ransom payment.
  • Ransom demand: 0.02 BTC (≈ US $500-800 static) – intentionally low to encourage quick pay; affiliate likely keeps 80 %.
  • Negotiation: e-mail ithelp01@onionmail[.]org plus Tox-ID inside note – 72-h countdown timer, then threatens “$ x 2”. Historical data shows 20 % of victims who paid received a working decryptor, others ignored.
  • Unique characteristic: Drops lightweight Python script (dst_prop.py) on Linux, re-uses nohup for resilience – rare for small actors.
  • Detection rule (Sigma – file creation)
    title: DST Ransomware Marker
    - FileCreation|endswith: '.dst'
    - FileName: 'HOW_TO_BACK_FILES.txt'

Key takeaway: Patch public-facing apps and lock RDP; 2022 victims whose ID ends in “t1/t2” can still get their data back today with Emsisoft’s free tool. Everyone else – rely on clean, tested backups; decryptor for online keys does not yet exist.

Share widely, stay safe, and back-up offline!