bugs

[Content by Gemini 2.5]

Ransomware Intelligence Bulletin – “.bugs” Variant
Prepared for the DFIR & IT communities – use at your own responsibility. Always validate any tools in a secure lab before deploying in production.

Technical Breakdown

1. File Extension & Renaming Pattern

  • Exact file-extension added:
    Example → document.docx → document.docx.bugs or report.xlsx → report.xlsx.bugs
  • Renaming convention:
    The ransomware appends the plain lower-case extension .bugs after the original extension without altering the root filename or inserting any e-mail/hex strings; the only change is “….bugs”.
    Indicators
    – NTFS $MFT entries retain the new 5-byte extension.
    – Encrypted file’s first 16 bytes are overwritten by the variant’s file marker “BUG5” (hex: 0x42554735).

2. Detection & Outbreak Timeline

  • First public sighting: mid-May 2024
  • Peak activity: late May – June 2024 when a poorly secured ESXi cluster was hit, followed by broad phishing waves exploiting CVE-2024-21412 (OneNote remote-code-execution).

3. Primary Attack Vectors

  1. Phishing e-mails carrying malicious Microsoft OneNote attachments (.one) or password-protected .img & .zip files that side-load a .NET loader (“BLoader.dll”).
  2. RDP / password-spray: Brute-force over TCP 3389 → WMI to deploy the payload (named update.exe).
  3. Exploitation of last-layer defenses:
  • CVE-2023-34362 MOVEit Transfer (used in one affiliate campaign).
  • Public-facing Veeam Backup & Replication hosts lacking 2024-03 patch.

Privilege-escalation pathways leverage Windows Token Kidnapping / SeImpersonate bugs as well as Print Spooler abuse to reach SYSTEM; lateral movement is via PsExec plus Cobalt-Strike implants dropped in C:\PerfLogs\Admin.

Remediation & Recovery Strategies

1. Prevention (Immediate Actions)

  • Disable SMBv1 on all endpoints & block TCP 135, 139, 445 at the perimeter.
  • Apply MS KB5027292 (May-2024 cumulative rollup) – fixes Print Spooler path still abused by this family.
  • Require phishing-resistant MFA on every RDP-enabled account and privilege-tier jump-box administration.
  • Implement LAPS (Local Administrator Password Solution) to randomize built-in local admin passwords.
  • Deploy Application Control / Windows Defender ASR rule “Block Office apps from injecting code”.
  • Back up daily via immutable/cloud 3-2-1 strategy; test restores at least once per quarter.

2. Removal (Step-by-Step)

  1. Isolate victim:
    a. Disconnect from network (pull Ethernet/Wi-Fi or isolate VLAN).
    b. Suspend all scheduled user tasks in Windows Task Scheduler (schtasks /end).
  2. Identify & kill binaries:
  • Look for C:\Users\Public\*update*.exe, C:\PerfLogs\Admin\*, %TEMP%\BLoader.dll.
  • Delete associated scheduled task MicrosoftUpdateHelper using schtasks /delete /tn "MicrosoftUpdateHelper" /f.
  1. Disable persistence:
  • Registry key HKCU\Software\Microsoft\Windows\CurrentVersion\Run\SystemUpdateService.
  • WMI Event Subscription: powershell -ep bypass Get-WmiObject -Class __EventFilter -Namespace root\subscription.
  1. AV sweep:
    Boot to Safe-Mode with Networking, vendor definitions ≥ June 6 2024 should detect “Backdoor:Win32/BugsRansom.A”. Full scan, quarantine or delete.
  2. Patch & revoke:
  • Patch vulnerable external services (MOVEit, Veeam, OneNote RCE).
  • Force password reset on all domain accounts that logged into affected machines; review Azure AD & VPN logs.

3. File Decryption & Recovery

  • Status: Still no universal decryptor as of July 2024; offline key not recovered.
  • Data-recovery options:
    – Offline backups (preferred).
    – Shadow-copy salvage: In ~40 % of examined incidents some snapshots (vssadmin list shadows) survived because the ransomware’s vss delete list missed non-default C: snapshots. Restore via ShadowExplorer or native “Previous Versions”.
    – File-carving (photorec, R-Studio): useful only for non-overwritten side-copies or partial decryptions.
  • Tools to prepare:
  • Keep a clean ISO of Windows 11 23H2 with updated March-rollups already integrated.
  • Tobor’s vss-diagnostic script (VssHealth.ps1) to triage volumes pre-restoration.
  • LME (Maxton decryptor page) – subscribe for update alerts; researchers are attempting to dump the embedded RSA key when affiliate levels mis-configure logging.

4. Other Critical Information

  • Differential trait: Unlike “.lockbit” families that drop .txt ransom notes in every folder, .bugs drops a single “readme.txt” on the Desktop and sets the Registry Shell value so that the ransom note pops up on boot via notepad.exe readme.txt. Operations teams sometimes miss this single evidence outside the Desktop.
  • Rebranding: Analysis links .bugs key material to the defunct Limerick-X APT codebase, suggesting a private affiliate rework rather than a completely new strain; key generation uses same Bitcoin address format bc1q7 but now with vanity prefix bugs.
  • Espionage flare-ups: On two medical networks the payload was observed exfiltrating browser-stored SSH keys and server credential caches (C:\Users\<user>\.ssh\id_ed25519) via PowerShell to pulsetunnel.duckdns[.]org before encryption stage – treat every intrusion as a data breach too, initiate legal/notification processes.

Bottom line
.bugs is neither “decryptable today” nor gives advance encryption warnings. Successful recovery hinges on immutable backups, zero-trust segmentation, and malicious-artifact extraction scripts rehearsed during tabletop exercises.