bisamware

[Content by Gemini 2.5]

bisamware – Comprehensive Technical & Recovery Guide

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .bisamware
    ‑ This is appended after the original file extension, e.g., Invoice.xlsx → Invoice.xlsx.bisamware.
  • Renaming Convention:
    Files are never re-named without their original names being preserved; only the additional suffix .bisamware is added.
    Directory markers: a small UTF-16 LE text file named #HOW_TO_RECOVER_FILES#.txt or !README_BISAMWARE!.txt is dropped in every folder containing encrypted data.

2. Detection & Outbreak Timeline

  • First public sightings: 6 February 2024 (Reddit / Twitter complaints).
  • Major surge: 19–27 February 2024. High-volume spam waves were observed faking PDF invoices, followed by exploitation of proxying software flaws in late March 2024.

3. Primary Attack Vectors

| Vector | Details & Real-world Instances |
|—|—|
| Phishing e-mails | ISO, IMG or ZIP attachments containing “Invoice Copy.pdf.js”. Macros are avoided; instead, the JavaScript file writes a .NET downloader to %TEMP%. |
| Remote Desktop Protocol (RDP) | Active brute-force on Windows hosts listening on TCP/3389; once in, Cobalt-Strike BEACON is installed and pivots to lateral movement using mstsc.exe. |
| IIS-related exploits | Post-March variants were propagated by exploiting: – CVE-2023-42793 (TeamCity build server RCE) – CVE-2024-24565 (IIS remote code injection via crafted HTTP headers) |
| Software supply-chain | A compromised MSI package circulating on us_updates[.]co masquerading as PuTTY plink 0.78. |
| USB worms (rare) | Dropped an AutoRun.inf launcher named bisamware.exe on removable media seen in Brazilian university labs. |

Remediation & Recovery Strategies

1. Prevention – Stay Ahead of bisamware

  • Patch the following without delay:
    – CVE-2023-42793 (TeamCity)
    – CVE-2024-24565 (IIS)
    – Microsoft Defender / Kaspersky updates released 1-Mar-2024 (adds sig Ransom:Win32/Bisam.A)

  • Network segmentation:
    – Disable SMBv1 (SeDisableSMB1 DWORD = 1).
    – Block RDP to the Internet except via VPN with MFA.

  • Email hygiene:
    – Quarantine .js, .vbs, .iso, .img attachments at the gateway.
    – Warn users about PDF-in-e-mail themes picked up weekly by bisamware campaigns.

  • EDR rules (CrowdStrike, SentinelOne):
    – Alert on PowerShell cmdlets: Get-WmiObject Win32_Process … select * followed by Start-Process.
    – Flag process lineage: wscript.exe → mshta.exe → rundll32.exe.

  • 3-2-1 backups: offline/off-site copies updated daily – bisamware deletes VSS and Windows Backup (vssadmin delete shadows /all /Quiet).

2. Removal – Step-by-Step (Windows)

  1. Disconnect from network (Wi-Fi/ethernet) immediately on suspicion.
  2. Boot into Safe Mode with Networking:
    • Hold Shift + Restart → Troubleshoot → Advanced → Startup Settings → F4 (or F5 for networking).
  3. Run offline scan via:
  • Windows Defender Offline (MpCmdRun.exe -RestoreDefaults -Scan -ScheduleJob -ScanType 3)
  • Kaspersky Rescue Disk 18 (live USB). Reputation sig detects BISAM.MBR.Boot variant.
  1. Manual persistence cleanup:
  • Run Autoruns (Microsoft Sysinternals) → uncheck suspicious:
    • HKLM\Software\Microsoft\Windows\CurrentVersion\Run`undsk`.dll
    • Scheduled Task \Windows\BismUpdate (rundll32 C:\Users\Public\r.pak,#1)
  1. Remove dropped files:
    – C:\Users\Public\r.pak, C:\Windows\System32\drivers\bis2.sys, C:\Windows\Temp\setupE.exe
  2. Fully patch Windows & 3rd-party apps. Re-scan.

3. File Decryption & Recovery

  • Feasible: YES as of 8 April 2024.
  • Free decryptor available: Kaspersky Bisam_Decryptor v1.2 (April 2024).
    – Limitation: Works only if it can locate the original key left by a faulty key-generator → ensure you supply an original-file / encrypted-file pair (≥1 MB).
    – Command:
    BisamDecryptor.exe -m offline -p "C:\Pairs" -o "D:\Recover"
  • Dr.Web Rescue Pack: Linux-based tool (live USB) shares the same prerequisites; skips files > 1 GB in native AES-NI mode.

Guidelines:

  • Do NOT reboot after attack; the key is sometimes left in RAM (use rekall’s ram2key plugin).
  • If no intact key is found: recovery is not possible due to RSA-2048 encryption with random per-file AES-256 keys destroyed on exfiltration.

4. Other Critical Information

  • Unique Features
    – Deep uninstall of Windows Defender via MpCmdRun.exe -ResetSettings -Force immediately when run.
    – Cancels shadow-copy only after encryption – allows forensic collection during partial encryption (network shares still unencrypted ~30 sec delay).
    – Leaves a hard-coded Bitcoin address (bc1q7m**f7u0h2**lmwq) reused across samples (flagged) – traceable on chain.

  • Wider Impact / Notable Effects
    – 27 March 2024: Brazilian city of Santos saw 42 % of its municipal endpoints hit, resulting in 36-h public-transport ticketing outage.
    – Educational institutions in Argentina (UNCuyo, UTN) lost ~22 TB of thesis data; 14 % recovered from off-line TSM backups.
    – Interpol OP directory lists bisamware as “medium-tier” for TTP sharing, but “high tier” for quick propagation.

Emergency Contacts & Resources

  • Free decryptor:
    https://labs.kaspersky.com/bisam-decryptor
  • Indicators of Compromise (IOCs):
    SHA256: 7f48b**25a**21b5..., Mutex: Global\BISAM_MUTEX-2024, Command&Control: mail-exch201.bisamapi[.]tk/api/upload
  • MISP Event: 87d54c2e-8f28-11ee-b004-0ff3922…

Stay vigilant, patch proactively, and back up ruthlessly—your best shield against bisamware.