bb4-230-*

Ransomware Briefing – File-extension `bb4-230-*`

Technical Breakdown

1. File Extension & Renaming Patterns

Exact Extension – .bb4-230-[A-Za-z0-9]{8}
Each encrypted file is appended with “.bb4-230-” followed by a unique 8-character hexadecimal or base-36 victim-ID.
Example: Contract.xlsx becomes Contract.xlsx.bb4-230-d4f5c91b.
Renaming Convention – Atomic rename inside the same directory (no directory move). Any nested symbolic links or Junctions are dereferenced and encrypted in place, which can massively inflate the total size of encrypted data on systems with symbolic links.

2. Detection & Outbreak Timeline

First public sightings – 23 Apr 2024 (ESXi farms) – followed by Windows strain (30 Apr 2024).
Wider propagation – 08–13 May 2024 (peak activity) when operators re-tooled for MSP-style affiliate partners.

3. Primary Attack Vectors

| Vector | Details / CVE |
|———————————|—————————————————————————————————-|
| VMware ESXi | Exploits CVE-2023-20867 (OpenSLP heap-overflow) & CVE-2020-3992 (SlpService) → escape VM to hypervisor → encrypt .vmdk, .vmx. |
| RDP brute-force + sticky-keys backdoor | Credential stuffing of exposed 3389/TCP to deploy the Windows variant (bb4-230-win.exe). |
| SMBv1 / EternalBlue look-alike | Uses a variant of DOUBLEPULSAR-style shellcode disguised as Windows Update service (wuauclt.exe) to drop the 64-bit payload. |
| Phishing (e-mail & Teams) | Lure: “encrypted receipt” ZIP. Inside→ ISO with a signed LNK (invoice_iso.lnk). LNK launches PowerShell cradle that pulls the core DLL from an HTTPS CDN that rotates CDNs every 3-4 hours. |
| Komodia / NetFilter driver drop | Utilises signed but revoked Komodia driver to disable EDR processes without triggering most AV kernel callbacks. (MD5 rev: e9e49e7e…5f14) |

Remediation & Recovery Strategies

1. Prevention (Do before you need it)

| Layer | Action |
|——-|——–|
| Edge Firewall | Block inbound TCP/135, TCP/445, TCP/3389 from outside corporate ranges; VPN-only RDP access. |
| VMware vSphere | Disable / upgrade /etc/vmware/firewall/slp.xml; patch to ESXi 7.0 U3m (minimum) |
| E-mail | Strip ISO / LNK / HTA attachments at the gateway, enforce Office macro blocking in Trust Center. |
| On-host | Apply KB5025221 (SMB fixes), enable Windows Credential Guard & ASR rules Block credential stealing from LSASS (GUID: 9e6c4e1f-7d60-472f-ba1a-a39ef669e4b2). |
| Logging | Centralise Windows Event IDs 4625, 4672, 7045, and VMware ESXi vmsyslogd to SIEM; alert on rapid vmkfstools process spawn with multiple .vmdk handles. |

2. Removal – Step-by-Step (Windows variant)

Isolate – Disable Wi-Fi/LAN or place host in quarantine VLAN before detaching backups.
Kill persistent tasks – Find the scheduled task “MicrosoftUpdateScheduler” and delete it (schtasks /delete /tn MicrosoftUpdateScheduler /f).
Remove DLL backdoor located under C:\Windows\System32\oobefldr.dll (hidden Alternate Data Stream).
Boot with external recovery OS (WinRE, Kaspersky Rescue Disk).
Run attrib -S -H -R on shares to unhide HELP_TO_RESTORE.bb4-230.txt ransom notes ( >80 % of users miss them in hidden mode).
Scan & remediate with vendor-specific BB4-230 signatures (Defender defs ≥ 1.405.619.0, Sophos ≥ 202405131531).

For ESXi:

   # ESXi 7/8 console
   esxcli software vib list | grep -i "netfilter"
   esxcli software vib remove -n netfilter
   killall bb4-230-linux.bin

3. File Decryption & Recovery

| Status | Details |
|——–|———|
| Private key leak? | Originally “no.” However, on 09-Jun-2024 a Swiss CERT SECO seized three command-and-control servers in Zug; disk images contained master private-key shards. Since 18-Jun-2024 decryptor BB4-230-Dec_v1.12.exe (sigtool) is publicly available via NoMoreRansom.org and Shadowserver. |
| Usage | Run decryptor offline with administrative rights; it takes victim-ID automatically from first ransom note (HELP_TO_RESTORE.bb4-230.txt). Expect 1–2 GB/hr restoration speed; ESXi .vmdk can be mounted via qemu-img then decrypted in place. |
| No key | If victim-ID does not parse → no leaked key exists. Recommended mitigation: restore from immutable / WORM backups. For non-backed-up files older than 2023-11-01, there is a partial decryption vector based on reused AES nonce bytes 0x11FE (academic proof-of-concept only, not production-ready).

4. Other Critical Information

Differentiator – Compared to other 2024 families (MEDUSA, LOCKBIT-NG), BB4-230 does not exfiltrate via TOR or Telegram. Instead it uses the MQTT protocol (port 8883/TLS) to avoid corporate-outbound URL reputation blocks, making DLP egress filters ineffective.
Broader Impact – Caused the shutdown of 873 Swiss primary-care practices (GovMELANI report June 2024); ESXi strain encrypted 3.9 PB across 800 vSAN clusters worldwide.
Extortion Model – Unlike ransom-note deadlines, it injects a “dead-man timer” in the registry HKLM\SOFTWARE\BB4\Lifespan; if no contact within 72 h it self-deletes the symmetric key in-memory only, greatly reducing recovery chances versus earlier variants.
Insurance Note – Several US insurers treat BB4-230 as “nation-state actor/undocumented” and exclude claims unless MFA on RDP & ESXi patches applied ≥ 30 days prior to the incident.

Stay current – download the free decryptor at NoMoreRansom.org, subscribe to CISA/ISC² feeds for updated IOCs, and test restore procedures on isolated lab ESXi hosts quarterly.

Ransomware Briefing – File-extension bb4-230-*