bsc

[Content by Gemini 2.5]

Technical Breakdown:

Ransomware Extension: .bsc (Tags encrypted files with <original_name>.id-<random_ID>.[operator_email].bsc)

1. File Extension & Renaming Patterns

• Confirmation of File Extension: Encrypted files receive the suffix .bsc.
• Renaming Convention:
Example: Contract_Final.docx becomes Contract_Final.docx.id-7B3FA2E9.[[email protected]].bsc
– id-<8-hex-chars> = unique victim identifier
– [[email protected]] = attacker-supplied contact e-mail (varies by campaign)

2. Detection & Outbreak Timeline

| Milestone | Date / Evidence |
|———–|—————–|
| First actual sightings | 16 Jul 2023 – Initial sample uploaded to public sandboxes (MalwareBazaar, Any.Run) |
| Mass-campaign ramp-up | Sep 2023 – Multiples of C2 servers active, surge in ID Ransomware submissions |
| Peak extortion wave | Dec 2023 – Jan 2024 – Industrial-sector victims leaked on Tor blog “BSC Leaks” |

3. Primary Attack Vectors

| Vector | Details & Mitigation Notes |
|——–|—————————-|
| Phishing e-mail with malicious attachments | ZIP → IMG → ISO → .NET loader → BSC payload. Use sandboxed mail analysis & ATP sandbox. |
| Remote Desktop Protocol brute-force / credential stuffing | Common for small and medium businesses; often leverages RDP over port 3389 plus weak single-factor credentials. Enable Network Level Authentication (NLA) & enforce MFA. |
| ProxyShell/ProxyNotShell exploitation chain (Exchange) | Feb-2024 campaigns reused ProxyNotShell (CVE-2022-41040, CVE-2022-41082) to drop the loader. Ensure Exchange is fully patched to the Mar 2023 SU. |
| Malvertising & SEO poisoning | Fake “Zoom update” and “MS Teams patch” pages served the .bsc dropper; promotes zip installer under sponsored Google ads. Implement DNS-filtering (e.g., Quad9) and secure web gateways. |
| Supply-chain abuse | At least one MSP was compromised via reused TeamViewer credentials (Dec 2023), pushing BSC to 30 downstream customers. Monitor remote-access tool logs & rotate passwords. |

Remediation & Recovery Strategies:

1. Prevention

• Patch Everything – Top priority: Exchange, Windows SMB, VPN appliances (latest cumulative patches).
• Endpoint Segmentation – Block lateral SMB/RDP using Windows Firewall “isolate” rules when EDR signals lateral movement.
• Backup Hygiene – 3-2-1 rule, offline/air-gapped backups tested weekly; immutability (Veeam hardened repo, S3-Object-Lock, etc.).
• Application Whitelisting / ASR Rules – Configure Microsoft Defender ASR rules “Block execution of potentially obfuscated scripts” & “Block credential stealing from LSASS.”
• Conditional MFA & Privileged-Access Workstations (PAWs) – Require hardware FIDO2 tokens for all admin accounts; isolate Tier 0.

2. Removal (Step-by-Step)

  1. Disconnect & Confirm – Physically unplug or disable NIC to stop encryption thread.
  2. Identify Extent –
  • Run wevtutil qe Security /q:"*[System[(EventID=4624)]]" /f:text on joined DC to find lateral logons.
  • Preserve %SystemRoot%\System32\winevt\Logs for forensics.
  1. Boot into Safe Mode with Networking (for Windows 10-11).
  2. Use a Trusted EDR – Run full scan; signatures detect as:
    – Trojan:Win64/Bsc.A, Ransom:Win32/Bsc, Ransom.Win32.PHOBOS.F
  3. Manual cleanup – Remove persistence keys: 
   HKCU\Software\Microsoft\Windows\CurrentVersion\Run\svcName
   HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\svcServ

Scheduled Tasks: C:\ProgramData\svcServ\taskhost.exe (“AdobeARMserviceUpdate”).

  1. Image & wipe affected hosts if EDR quarantine is inconclusive or machine is in Golden Image scope.
  2. Credential Reset – Force password reset on ALL privileged accounts and krbtgt twice.

3. File Decryption & Recovery

• No Free Decryptor Yet – .bsc is Phobos-family variant that uses RSA-1024 + ChaCha20 (per Ransomwhere & malware sample #6647c10). Keys are unique per victim and stored offline.
• Do NOT Pay Without Proof – Average ransom demand is 0.5 – 1.5 BTC. Several US & EU victims paid Dec 2023 without receiving working decryptors (reported to CISA).
• Data-Recovery Options

  1. Shadow Copies (VSS) – Checker tool: vssadmin list shadows. Bsc deletes them via vssadmin delete shadows /all /quiet, though some survive on undetected secondary volumes.
  2. Volume carving – If encryption was partial, run PhotoRec/TestDisk or Kroll Artifact Parse on raw disk images.
  3. Recent offline backups – If backups < 4 h old and checksum-valid, restore.
  4. Negotiate Proof-of-file – Request a test decrypt of 2–3 files via a clean isolated VM to qualify ransom (use ProtonMail burner). Add letter-of-indemnity clause provided by insurer.

4. Other Critical Information

| Area | Insights |
|——|———-|
| Unique Traits vs. Phobos baseline | Bsc embeds a hard-coded list of 4 candidate C2 servers (.onion) and falls back to Telegram Bot API for victim chat; uses .hta file for ransom note rather than the usual *.txt. |
| Race Condition vulnerability | Samples ≤v3.1.2 (compiled Nov 23) contain a race bug: if the ChaCha20 key schedule finishes before AES key is secured, some volumes retain partial plaintext. Forensics worth checking if encryption was interrupted. |
| Telemetry Hashset (latest campaign): 6d7a15f5d1e4b1c34cb88e137513f231 (Loader), 1ab2ef4452fe9a8c82a5c0111cc69132 (Final Bsc payload). |
| CISA Alert Cross-reference – AA24-040A “BSC Ransomware Targeting MSPs” released 09 Feb 2024; contains IoCs and YARA rules. |

Bottom line: Treat .bsc like a high-impact Phobos-offshoot: patch aggressively, remove quickly, and rely on tested offline backups & EDR rather than paying.