[email protected]

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‼️ Hard-Clarification

The string [email protected] is the attacker-controlled e-mail address used by the Dharma / CrySiS family of ransomware—not the file extension.
For that reason this write-up targets the Dharma / CrySiS variant that utilizes the contact address [email protected].

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Technical Breakdown

1. File Extension & Renaming Patterns

• Confirmed File Extension Sequence(s):
  .id-[8-char-random-id].[[email protected]].{original-ext}
  Example → document.docx.id-A1B2C3D4.[[email protected]].docx
• Earlier Releases sometimes dropped the square-bracket envelope:
  [email protected].
• Renaming Hierarchy:

1. Encrypts and renames file in-place with the new multi-part extension.
2. Runs a one-time wipe of Volume Shadow Copies (vssadmin delete shadows /all).
3. Drops README.txt / Info.hta recovery notes in every affected directory.

2. Detection & Outbreak Timeline

• First Sample Submission (Dharma w/ [email protected]): October–November 2017, shortly after early 2017 Dharma leaks.
• Peak Waves:
  • April 2018 – SMBv1 lateral-movement campaigns.
  • Q4-2019 spike – Remote Desktop Services exploitation amid COVID work-from-home migration.
  • Still appearing in limited numbers today.

3. Primary Attack Vectors

1. RDP Brute-Force / Credential Stuffing
   – Port 3389 directly exposed to the Internet.
   – Hacked or purchased credentials (distributed by gangs such as “Gold Temple”).

2. E-Mail Phishing With Weaponized Attachments
   – .zip → .exe or double-extension .pdf.exe.
   – MBRLockers rarely used; multi-layer payload downloads done by PowerShell or HTA.

3. Exploit Kits (older cycles)
   – RigEK, GrandSoftEK occasionally dropped Dharma loaders.

4. Third-Party Tool Compromise
   – Supply-chain infection via trojanized software updaters or MSP products.

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Remediation & Recovery Strategies

1. Prevention

• Network Hardening
  – Disable Remote Desktop on endpoints unless under strict VPN w/ MFA.
  – Use Group Policy to enforce a minimum RDP encryption level (TLS 1.2).

• System & Service Configuration
  – Patch CVE-2019-0708 (“BlueKeep”) and CVE-2020-1472 (“Zerologon”) immediately.
  – Disable SMBv1 server-wide.

• Access Controls & Awareness
  – Enforce strong, unique RDP passwords (12+ chars).
  – MFA token + lockout after 3 failed attempts.
  – Educate users to report any e-mail with double extensions or encrypted archives.

2. Removal (Post-Infection Step-by-Step)

1. Isolate the host physically or via SOC automation.
2. Clone / Image disk for forensic chain-of-custody (many LE/IC task-forces can trace Bitcoin payout address patterns).
3. Boot into Safe Mode + Networking.
4. Delete persistence mechanisms:

• Scheduled task (C:\Windows\System32\tasks\IERunner, WindowsHelper, etc.).
• HKLM / HKCU Run keys pointing to randomly named executables under %APPDATA%\Roaming\ or C:\ProgramData\.

1. Run modern endpoint-protection agent offline scan (ESET, Bitdefender, Kaspersky, Sophos—all have Dharma signatures).
2. Verify removal: no new renaming events, no return of Info.hta.

3. File Decryption & Recovery

• Decryption Feasibility: YES—but only IF you have original files that were encrypted by the pre-May 2017 master key leak.
  – Use the free Kaspersky / Emsisoft Decrypter for CrySiS/Dharma (updated Nov 2021).
  – Limitation: does not cover post-April 2018 strains deriving keys per victim.
• Brute-force / smart-recovery tools (undelete, file-carving) can restore partially overwritten media, but AES-256 is otherwise impervious.
• Restore from offline / immutable backups (Air-gapped, WORM, cloud-object lock) → quickest before paying.

4. Other Critical Information

• Ransom Amount: Usually 0.5–1.8 BTC (dynamic exchange pricing). The subject line frequently contains “All your data is encrypted by ransomware .dharma!”—a quick heuristic filter.
• Data Leak Sites: Dharma operators historically partner with other extortion groups; if lateral movement reached NAS shares, tiered ransom demands can include threats of release.
• Mitigation Toolset–Windows 10/11:
  – Enable “Controlled Folder Access” (Windows Defender ASR rule).
  – Turn on the Windows Backup + OneDrive known-folder-move (ask clients to configure retention >30 days).
• Law-Enforcement Coordination: Submit encrypted sample hashes (always SHA-256 when possible) to ID-Ransomware/CJK or your national CERT for IOC correlation.

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Bottom Line

The [email protected] e-mail handle signifies a persistent Dharma branch. With no master-key reliance beyond mid-2017, a modern dual-prong defense—hardened RDP + solid immutable backups—remains the single most effective countermeasure.