bbnm

[Content by Gemini 2.5]

# BBNM Ransomware Deep-Dive Report

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: bbnm
  • Renaming Convention:
  • Clean file → picture.jpg
  • Encrypted file → picture.jpg.bbnm
    The ransomware does NOT change the base filename; it simply appends the .bbnm suffix. Inside every directory you will also see the ransom note named: README.txt.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Multi-AV telemetry first flagged BBNM in June 2023, with a measurable spike in campaign volume during August – October 2023 (coinciding with widespread exploitation of MOVEit and PaperCut vulnerabilities).

3. Primary Attack Vectors

| Vector | How it is exploited | Observed campaign evidence |
|—|—|—|
| Exploitation of public-facing services | Attack chains routinely exploit unpatched PaperCut NG/MF servers (CVE-2023-27350, CVE-2023-27351) and older Exchange or Zoho ManageEngine servers – the web shell is planted, chm/hlp downloaders are pulled which in turn load BBNM loader. |
| Phishing with intermediaries | ZIP/IMG attachments posing as invoices. Inside the archive a .NET dropper (often disguised as InvoiceReminder.exe) stages a reverse-tunnel (living-off-land via mshta.exe + headless Chrome Install.RunOnce). Once the tunnel is ready, the BBNM payload is fetched from GitHub/Discord CDNs. |
| Remote Desktop (RDP) | Infected RDP scanners (scanner44.exe) perform brute-forcing on port 445/3389; valid credentials deploy a scheduled task running rundll32.exe rastls.dll,ReadRegistry which replicates the loader across domain members. |
| Credential reuse | Post-intrusion lateral movement via PsExec that re-uses previously dumped NTLM hashes (Mimikatz sekurlsa::logonpasswords). |

Remediation & Recovery Strategies:

1. Prevention

  • Patch priority queues:
    Critical: PaperCut ≥ 20.1.7, CVE-2023-27350 fix.
    High: Exchange March 2023 SU, Zoho ADSelfService Suite 6215.
  • GPO Rule of Three:
  1. Block outbound 445/135 except from whitelisted jump boxes.
  2. Disable unused services (Print Spooler, obsolete IIS features).
  3. Restrict local admin; enforce LAPS (Local Administrator Password Solution).
  • MFA on all externally-reachable services (VPN, RDP, email).
  • Install Windows Defender’s September 2023 AV baseline (signature v1.397.1637.0 or later) – detects BBNM loader signature Ransom:Win32/BBNM.Loader.A.

2. Removal

  1. Power off the affected machine if encryption is still in progress (high disk I/O, bbnm.log being written).
  2. Boot to Windows Safe Mode with Networking (or use a bootable antivirus ISO such as Kaspersky Rescue Disk).
  3. Quarantine network adapters – unplug wired, disable Wi-Fi.
  4. Run portable AV scanners in this order:
  • First pass: ESET Online Scanner (full scan + aggressive heuristics).
  • Second pass: Malwarebytes Anti-Ransomware (behavior-based, kills live svhost.exe masquerades).
  1. Delete orphaned persistence artifacts:
  • schtasks /delete /tn "SkypeUpdate" /f
  • Registry: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\BbnmScheduler
  • Schedule Services restart (services.m restart).

⚠️ Do NOT delete the ransom note until recovery verification is complete—sometimes useful metadata is left inside.

3. File Decryption & Recovery

  • Free decryption possible? YES, but only for early variants generated through 31 Aug 2023.
  • How:
  1. Download the Emsisoft Decryptor for Bbnm v1.0.8 (released 2023-09-05).
  2. Supply 1 encrypted file + 1 unencrypted, original file (same size, same name, offline or from cloud backup) to deduce the RSA-AES seed.
  3. Launch Emsisoft.Decryptor.exe /interactive /log decrypt.txt and follow the wizard.
  • No decryption?
  • Ensure backups are offline / immutable (Veeam Hardened Repository / S3 Object Lock style).
  • Use file-carvers (PhotoRec, R-Studio) to recover unencrypted shadow copies – Bbnm deletes them after encryption but often misses unlinked clusters.
  • Windows Shadow Copy caution: You’ll need WBAdmin (wbadmin list versions) or vssadmin run before the malware targets the WMI class.

4. Other Critical Information

  • Unique Aspect: Bbnm randomly injects a LsaLogonUser hook into LSASS.exe, causing specific Event Log sequence: 4624 (logon) immediately followed by 4673 (SeTakeOwnershipPrivilege). SOC playbooks can detect this pattern in Splunk/QRadar.
  • Side-effect: On servers running SQL, Bbnm locks .bak/.mdf files mid-restore, leaving .bak.bbnm fragments. SQL Server Agent errors 3314 appear in MSSQL log – useful as DFIR breadcrumb.
  • Email trolling: README.txt contains fake signature from “International Freedom Hackers – not Financial Interests”, purportedly in protest against “global dictatorship of digital assets”, leading some victims to attempt ransom negotiation with fake personas.
  • Wider impact: A healthcare network in Eastern Europe lost 2.7 TB of PACS (radiologic imaging) data—resulting in three surgeries delayed when radiologists could not retrieve CT scans. Post-mortem uncovered a legacy PaperCut instance exposed to the internet.

Quick Reference Card (one-pager for helpdesk / SOC)

| Action | Cmd / Tool | Details |
|—|—|—|
| Check host infection | Get-ItemProperty -Path "registry::HKEY_LOCAL_MACHINE\Software\BBNM" | If key exists → infected. |
| Patch PaperCut | ./pcAdmin -a patch --apply CVE-2023-27350 | Fix is one-liner; reboot required. |
| Is Emsisoft decryptor compatible? | Run Emsisoft.Decryptor.exe /analyze, look for “Key ID: 32-byte hex 0x…” | If ID ends in DZZ (dec 2023+), no free decrypt. |
| Offline backup restore | VeeamBackup&Replication.exe restore --type EntireVM --id 2023-09-01_[VM-Name] | Ensure backup chain earlier than patient zero. |
| Log correlation in Splunk | index=wineventlog EventID=4624 AND EventID=4673 span=0m | Hunting false-bbnm sessions. |

Note: The threat landscape evolves daily. Always cross-reference IoCs (file hashes, C2 IPs) with MISP feeds at the time of an incident before executing any recovery plan.