dcry

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .dcry
  • Renaming Convention:
  • The sample prepends an 8-byte hex string in lower-case to the original file name, followed by a dot, followed by the extension .dcry.
  • Example: notes.txt becomes a7fb9e10.notes.txt.dcry
  • Drives mapped as C:\, D:\, fixed-removable (USB), and all accessible network shares (UNC paths) are targeted.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
  • First public sightings (uploads to ID-Ransomware, Any-Run, and hybrid-analysis) on 7 March 2019.
  • A small resurgence was noted in August 2019 before public activity effectively disappeared.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  • Cracked software installers: Most prevalent initial vector seen in the spring 2019 wave. Common packages faked were Adobe Acrobat Pro, KMS-Auto activator, and WinRAR “full”.
  • Supposed “software-updater.exe” delivered via malicious Google Ads / SEO poisoning for popular utilities such as CCleaner and uTorrent.
  • RDP brute-force / credential reuse when the host is internet-facing (port 3389/TCP).
  • No evidence of worm behavior (EternalBlue, SMBv1, etc.); payload is single-stage, user-executed.

Remediation & Recovery Strategies:

1. Prevention

  1. Close TCP/3389 SMB/445 to the Internet; switch outside-in RDP to VPN or RDP Gateway.
  2. Enforce multi-factor authentication at any external entry point.
  3. Block AppData\Roaming\RandomDir\dcry.exe path by AppLocker / Windows Defender Application Control.
  4. Disable macro execution in Microsoft Office and maintain strict email attachment filtering.
  5. Keep offline, encrypted backups; implement the 3-2-1 rule and periodic restore drills.
  6. Patch OS & third-party apps aggressively (especially web browsers, PDF readers, remote-access tools).

2. Removal (Step-by-step)

  1. Isolate: Disconnect network/Wi-Fi to stop lateral movement.
  2. Create incident image: Forensic DD or Veeam-level backup before any reboot.
  3. Kill the process in Task Manager (usually dcry.exe or the random name from the temp directory).
  4. Remove persistence:
  • Check both registry HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
  • Also the 16-byte file inside C:\Users\Public\Database*.bin (contains startup script—delete it).
  1. Delete payload from %APPDATA%\system32\ and %TEMP%\ (look for date-stamped folder created today).
  2. Run a full scan with updated AV (all modern engines now have signature Trojan:Win32/Dcry, Ransom:Win32/DCry.A).

3. File Decryption & Recovery

  • Recovery Feasibility:
  • ** decryptable **. Kaspersky, Emsisoft, and Bitdefender have released free tools.
  • Decryptor Download & Use (Windows only):
  1. Download the most recent Emsisoft DCRY Decryptor (ZIP, SHA-256 verified: 1b38f0c4…).
  2. Place a pair of an original and an encrypted file on the desktop for key derivation.
  3. Run as Admin, press “Start”, choose the drive root, and let the decryptor run (expect ~1 GB/min, logs auto-exported to +decrypted.txt).
  • Essential Patches/Tools:
  • Microsoft Defender signature packs (July-2019 Update KB4507704).
  • Disable PowerShell v2 via “Turn Windows Features on/off” (the dropper uses v2 bypass obfuscation).

4. Other Critical Information

  • Unique Characteristics:
  • AES-256-CFB mode is used; the AES key is encrypted with RSA-1024 and appended to READMETORESTORE_FILES.txt.
  • If the attacker’s C2 returns HTTP 500, the sample falls back to a hard-coded weak public key (this is what Emsisoft exploited) – another reason offline hosts can still decrypt.
  • No file-type filtering; the ransomnote instructs victims to email [email protected], but the mailbox was taken down within 72 h of public release, strengthening the offline decryption path.
  • Broader Impact:
  • Primarily affected home users and small businesses in Europe & Latin America due to its distribution via pirated software ads.
  • Served as a proof-of-concept for criminals that even 100 % decryptable campaigns can yield quick cash; detection matured within weeks once IOCs were disseminated.

TL;DR: .dcry is an already-broken, March-2019 ransomware mainly spread through pirated ISO/EXE files. Remove it with standard AV cleanup, and unlock files using the free Emsisoft tool ‑ assuming you retain at least one unencrypted copy for key recovery.