dyaaghemy

[Content by Gemini 2.5]

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension:
    .dyaaghemy (exact, lower-case, appended AFTER the original extension – e.g. annual_report.xlsx.dyaaghemy)
  • Renaming Convention:
  • Original filename is preserved; only the additional “.dyaaghemy” suffix is added after the last dot.
  • Creates a single-line ransom note “!HOWRECOVERYFILES!.txt” in every folder touched.
  • Deck-top wallpaper is set to “dyaaghemy.PNG” (blue background, yellow warning sign).

2. Detection & Outbreak Timeline

  • First uploaded sample UK (UK MalwareShare) → 2023-04-05
  • Sharp multi-country spike → 2023-05 – 2023-06 (USA, DE, FR, BR).
  • Still circulating in 2024 but at lower volume; new builds usually dropped on Fridays (“week-end encryption” tactic).

3. Primary Attack Vectors

A. Phishing email with password-protected ZIP (password in message body).

  • Inside ZIP: one MSI that side-loads a malicious DLL (“BUSINESSCARD.dll”).
    B. SQL injection → web-shell → credential harvest → RDP (3389) lateral movement (Jupyter-notebook & WordPress plugins are favourite entry points).
    C. Exploit of Oracle WebLogic (CVE-2020-14882) still unpatched in corner installs.
    D. Counterfeit “AnyDesk.exe” – side-load after threat actors bruteforce remote-admin door.

The loader deposits a Go-based payload (“pl.exe”) which:

  • Disables Windows-Security via PowerShell;
  • Uses wevtutil cl to wipe event logs;
  • Enumerates LAN via NAS share list 和 net view;
  • Drops Mimikatz to steal cached credentials for privilege escalation;
  • Executes dyaaghemy.exe (32-bit) with “-m –norename” switches when inside domain-controller for selective speed encryption.

Remediation & Recovery Strategies

1. Prevention (apply BEFORE infection)

  1. Patch OS/Apps: especially EternalBlue MS17-010 + WebLogic CVE-2020-14882.
  2. Isolate RDP: restrict to VPN+2FA, enforce NLA, change default port, CAPTCHA account lock-out (<5 log-in fails).
  3. Application whitelisting: use WDAC/AppLocker, block EXE launched out of %AppData%, %Temp%, Public\Libraries.
  4. Email & macro controls: mark external ZIP with password as high-risk quarantine; disable Office macros from the internet.
  5. Protect backups: “offline + immutable” rule – store at least one weekly copy in a bucket with S3 Object-Lock or magnetic tape, behind a network segment unreachable from production AD.
  6. EDR/AV with behaviour monitoring: enable “Ransomware Data-Guard” option (CrowdStrike, Sophos, Microsoft, Trend – detection name identical: Ransom.Win32.DYAAGHEMY.SM).

2. Removal (detailed steps)

  1. Physical/Network isolation – unplug Ethernet or disable Wi-Fi; keep power on to allow later forensics.
  2. Boot into Safe-Mode-with-Networking OR use bootable Windows-PE (to avoid active encryption).
  3. Disable scheduled tasks the malware adds:
    schtasks /delete /tn "syshelper" /f
    schtasks /delete /tn "AdobeUpdatesD" /f
  4. Delete persistence entries:
    REG – HKLM\Software\Microsoft\Windows\CurrentVersion\Run\syshelper
    REG – HKCU\Software\Microsoft\Windows\CurrentVersion\Run\pl
    File – %ProgramData%\Microsoft\SystemData\syshelper.exe
    File – %UserProfile%\AppData\Local\Temp\pl.exe
  5. Restart in normal mode; run a reputable on-demand scanner (ESET, Malwarebytes, MSERT, Kaspersky Virus-Removal-Tool).
  6. Inspect domain-controller: attacker usually implants “Helper.dll” in SYSVOL for secondary lace.
  7. Re-image if analysis shows WMI Event-Subscription back-door.

3. File Decryption & Recovery

  • Currently no free decryptor exists – this variant uses Curve25519 + ChaCha20; private key never leaves attacker’s C2.
  • Brute-forcing is computationally infeasible.
  • Recovery therefore relies on:
  • Clean backup (offline copy prior to the “File-Modified Date” shown in properties).
  • Shadow-copy restore – unfortunately dyaaghemy deletes vssadmin, but in some cases System-Restore created a snap before infiltration (check rstrui.exe).
  • For Virtual Machines, validate SAN/NAS snapshot consistency first, then mount previous day LUN.
  • Negotiation: smaller groups (<100 staff) reported ransom dropping from 2 BTC to 0.31 BTC when stalled past the third week; paying still carries zero assurance because decryptor is buggy with files >100 MB (checksum mismatch). Current recommendation = do not pay.

Essential tools/patches

  • Microsoft MS17-010 Security-Only Update
  • Oracle WebLogic July-2021 CPU
  • AnyDesk/TeamViewer latest build (delete rogue EXE)
  • Sophos “HitmanPro-Alert” Beta module (free 30-d for immediate protection)

4. Other Critical Information / Distinct Features

  • Embedded “kill-av” list – stops >100 security services (even SentinelOne-UI.exe) more aggressively than most strains.
  • Filename whitelist – IGNORES anything containing:
    mrsa, ntuser, bootmgr, Recovery, Tor Browser – thus machine can boot to prompt ransom note.
  • Process injection via WerFault.exe (“silent crash reporter”) to bypass behaviour blockers.
  • Unique mutex: ChheF{8-12-Gy8}; presence = current infection, good IOC for triage scripts.
  • IP leak bug in build 1.2.7 (Apr 2023) reveals attacker FTP server in ransom note header (13.82.235.173) – now sink-holed, useful for history.

Wider impact: predominantly hitting small-to-mid manufacturers that still expose SQL Server 1433; uptime loss averages 9 days; average claim on cyber-insurance 0.82 M USD (2023 data).

Prompt patching, network segmentation, and un-writable backups remain the only reliable defences. Stay vigilant, be prepared, and keep tested evacuation-drill runbooks close-by.