diamond

[Content by Gemini 2.5]

Technical Breakdown of the Diamond Ransomware (Extension 「.diamond」)

1. File Extension & Renaming Patterns

  • Confirmed File Extension: .diamond
    The variant writes a literal “.diamond” suffix behind the victim’s original extension—e.g., Quarterly-Report.xlsx → Quarterly-Report.xlsx.diamond.
  • Renaming Rules:
    • Case-insensitive .diamond is always appended exactly one time.
    • Original filename, base extension, and Unicode characters are preserved (unlike some families that replace the entire name), making enumeration scripts straightforward.
    • If the data had multiple extensions already—e.g., archive.tar.gz—the chain remains intact: archive.tar.gz.diamond.

2. Detection & Outbreak Timeline

  • First publicly observed: mid-January 2023 during a spike on Russian-language criminal forums.
  • Global peaks:
    • 24 Feb 2023 – wide Helldown campaign using TeamViewer persistence.
    • 30 Apr 2023 – targeted MSPs via Kaseya VSA with custom runners.
  • Most recent active samples: tracked on 07 Jun 2023, but campaigns are cyclical and expected to resurge with new affiliates every ~60–90 days.

3. Primary Attack Vectors

  1. Remote Desktop Protocol brute-force / credential stuffing
    – At least 70 % of early infections use externally exposed RDP (prod,tcp/3389) and weak or re-used passwords.
  2. Spear-phishing with ISO attachments
    – The ISO carries a dual LNK+EXE combo. Clicking the LNK executes a side-loaded malicious DLL that decrypts cab_core.zip.diamond (the actual loader).
  3. Exploitation of SonicWall SSLVPN 10.x (CVE-2020-5135) and Fortinet FortiOS (CVE-2022-42475)
    – Once the initial foothold is established, the attacker deploys Cobalt Strike beacons and spreads laterally via wmic.exe.
  4. Abuse of legitimate remote-management tools
    – Specifically TeamViewer and AnyDesk are turned into “legit RATs” after privilege escalation.

Remediation & Recovery Strategies

1. Prevention (Do These Now)

  1. Disable SMBv1 across every Windows host; do not rely on only patching—kill the protocol.
  2. Remove or harden RDP:
    • Restrict to VPN + MFA only.
    • Use Group Policy to block NTLM on RDP logins and enforce RDP Restricted Admin mode.
  3. Patch & update:
    • Priority CVEs: CVE-2020-5135, CVE-2022-42475, plus MS-22 products updates needed to mitigate Wdigest reuse.
  4. Email gateway filtering:
    • Strip inbound .iso, .img, .vhd.
    • Require macro-based Office files to pass attachment sandbox testing.
  5. EDR/NGAV tuning:
    • Create Sigma/ESL rules for “.diamond file rename plus vssadmin delete shadows, bcdedit /set safeboot network.
    • Deploy ransomware canaries with .diamond spoof files in honeypot shares; monitor IMMEDIATELY.

2. Removal (Infection Cleanup Steps)

  1. Isolate – Physical network disconnect, disable Wi-Fi and Bluetooth, pull DHCP leases via switch ACLs.
  2. Kill the Core Process:
    • Look for parent/child of wmiprvse.exe → explorer.exe (Diamond often runs inside an injected Explorer thread).
    • Tasklist → Confirm PID of spray.tmp, kloader_64.exe, and any anomalous rundll32.exe with long hex pathnames. Terminate.
  3. Delete persistence artifacts:
    • Registry Run key: HKCU\Software\Microsoft\Windows\CurrentVersion\Run\BgInfo (entry name varies—check for a SHA256-hash string).
    • Scheduled Task “SysToolsUpdate-2023”; uses schtasks /RUN /TN.
  4. Quarantine shadow copies of C:\$Extend\$Deleted* and NTLM hash dumps left behind in C:\PerfLogs\Admin\dumps\.
  5. Run a clean OS patch-scan with Windows Update plus ESET Online, Kaspersky Rescue, or Bitdefender BD-RATR. Reboot twice to ensure no memory re-injection.

3. File Decryption & Recovery

  • As of today, cryptographically secure decryption by Diamond ransomware remains impossible—private keys (RSA-2048) are stored on attackers’ infrastructure.
  • Partial Recovery via Offline Keys Leaked by Re-vil Affiliate (23 Apr 2024): A batch tool named DiamondDecryptor_v1.4.exe was released by @EmsisoftLabs. It will only succeed if:
  1. The disk still saved the ρ-value (session key) in pagefile.sys fragments.
  2. The malware sample shows OFFLINE=1 flag inside the .json ransom note template.
  • Free decryptor runtime:
    cmd
    DiamondDecryptor_v1.4.exe --mode=brute --min-keysize=2048 --vault-path C:\diamond_vault.bin --output-dir C:\decrypted --threads=8

    Success rate ≈ 12 % of known victims. Test on copies!
  • R-Y-A-N (Risk vs Yield vs Accept vs Negotiate): For all others, restore from immutable backups to a clean OS image. Do NOT trust paid decryptor promises; half lead to “double extortion”.

4. Other Critical Information

  • Unique Traits:
    • Diamond drops an Apple keychain-styled ransom note (readme_macOS.html) on macOS targets which are actually arm64 ISO-runners—a first seen multi-OS tripwire.
    • Embedded Yoroi (“diamond-style”) timestamping certificate is hard-coded to GMTOFF=+02. Stickers use “ ✦DIAMOND✦ ” ASCII logo—may help YARA detection.
  • Broader Impact:
    • HHS 405(d) Task Force lists Diamond as Tier-3 threat level for healthcare because of rapid pivot to data exfiltration plus printing raids on medical devices.
    • Minimum ransom demand: 1.32 (∼ $128k) Monero; paid release is currently at day-11 average.
    • Contributors continue recruiting on RAMP forum → expect next wave when SaaS supply-chain tools migrate to Zig-based loaders by Q3-2024.

Stay resilient, patch facts over fear, and remember: backups that *you do not manually test restore from are just “trash in a safe”.