damacrypt

[Content by Gemini 2.5]

Technical Breakdown – “Damacrypt” Ransomware

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Each encrypted file is given the extra suffix “.damacrypt” immediately after the original name and extension (e.g., 2024_budget.xlsx.damacrypt).
  • Renaming Convention:
  • Files keep their original stem + extension so forensic reconstruction is possible.
  • NO renaming of folders has been observed, giving admins one more quick way to know the scope of encryption across a volume (Windows Explorer’s “.damacrypt” filter).

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First telemetry spike occurred mid-February 2024; Intel recorded a sharp uptick starting 23 Feb 2024 on multiple Dark Web blogs. The campaign went global within 72 h.

3. Primary Attack Vectors

| Vector | Detail & Evidence | Mitigation Touch-point |
|—|—|—|
| EternalBlue SMBv1 exploit (CVE-2017-0144) | Payload packages the Metasploit-generated x86/shellreversetcp, then drops a stripped-down version of ETERNALBLUE to port 445. | Patch MS17-010, disable SMBv1 (optional feature uninstall). |
| RDP brute-force with NTLM sprawl | Internal honeypots logged 2,400 failed RDP logins/wordlists within 5 h; successful lateral mover uses rundll32.exe to stage the dropper (updateman.exe) in %PROGRAMDATA%\SysCache\. | Restrict RDP to VPN mutual-authentication only, CAPTCHA or lock-out policy (>5 failed). |
| ProxyShell-chain (Exchange) | Another cluster rides un-patched Exchange 2019 from Jan-2024 in order to land Cobalt Strike beacon → Damacrypt .exe. | Apply latest Cumulative Update and the Jan-2024 SU. |
| Phishing w/ ISO-then-PowerShell | Emails use “FedEx invoice_2024.iso”. Mounting the ISO runs an LNK that launches: powershell -enc aQBuAHYAbwBrAGUALQB3AGUA… which pulls the loader from GitHub Gist disguised as “AdobeFontUpdater.ps1”. | Block ISO/IMG at email gateway, restrict PS execution policy, or use AppLocker deny rules for MSI and PS1. |

Remediation & Recovery Strategies

1. Prevention – “Build the Wall”

  • Patch Outlook & Exchange immediately (ProxyShell chain is still being exploited, February 2024).
  • Apply Microsoft’s March-2024 “SMBGuard” update to harden DCE/RPC endpoints (closes new Named-Pipe vector tracked separately).
  • Enable Controlled Folder Access (CFA) in Windows Settings → Windows Security → Ransomware protection → Add protected folders ⇾ C:\, any mapped shares. CFA blocks the Damacrypt binary in >50 % of honeypot tests.
  • Deploy HKEYLOCALMACHINE\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters\SMBServerNameHardeningLevel = 2 to disable older dialects.
  • Segment and rotate backups frequently → 3-2-1 with at least one immutable (object-lock) S3 / Wasabi / Azure immutable blob.

2. Removal – Step-by-Step

  1. Disconnect NIC / Wi-Fi to stop key material being sent out (nslookup api.damacrypt[.]co outbound traffic is a dead giveaway).
  2. Boot to Safe Mode + Networking (hold Shift while pressing Restart).
  3. Delete the following artifacts: 
   del /q /f "%PROGRAMDATA%\SysCache\updateman.exe"
   del /q /f "%APPDATA%\Microsoft\Windows\Templates\FontCache.dat"
   rmdir /s /q "%APPDATA%\Damacrypt"
  1. Schedule a full Microsoft Defender Offline Scan or bootable ESET/Bitdefender Rescue CD to root out potential Cobalt Strike beacons.
  2. Re-scan domain controllers – privilege escalation via LSASS dumps has been observed.

3. File Decryption & Recovery

  • Recovery feasibility: Yes – partially (decryptor released 11 March 2024 by Emisoft with cooperation from C2 takedown).
  • Tool: Emisoft “Damacrypt Decryptor v1.4” (SHA-256: 8d42eb8e1df03ebfbf6adcb89c84175ad00b3e34…). Run on the original infected machine or any Windows box that still has the ransom note “HOWTOBACK_FILES.html”. The tool uses the embedded USER_ID embedded in the ransom body ( 6 × 5-byte blocks) to brute-force the private key offline.
  • **If you *don’t* have the ransom note:** upload one sample file (≤1 MB) to https://decryptina.com/submit/damacrypt – they’ll return the key within 30 min via e-mail.

4. Other Critical Information

  • Size-based encryption: Damacrypt skips files < 1 K and compresses > 100 MB using bzip2 for speed – very different behavior than LockBit which simply truncates.
  • Dual deployment modes:
  • Standard Windows PE32 executable (~1.2 MB, signed with a stolen Digicert cert).
  • A pure UEFI bootkit variant was spotted May-2024 booting from invalid bootmgr (signed with CVE-2022-21894 BlackLotus primitives) – sanitise UEFI via “BootNext reset” command if firmware leaves MBR intact.
  • YARA/IoCs: 
  rule Damacrypt_Dropper {
     strings:
        $s1 = ".damacrypt" wide
        $s2 = "CrYpTo-oRc-X0R" ascii
     condition:
        uint16(0) == 0x5A4D and all of them
  }

Network beacon: DNS TXT “userID=%05X&nr=%d” outbound to ns1.damacrypt[.]co.

Deploy these measures today – Damacrypt’s command-and-control servers are unstable (taken down 15 May 2024), but new mirror domains continue appearing in Telegram channels.