babyk

[Content by Gemini 2.5]

Below is a single-source, defense-oriented reference sheet for the ransomware tracked internally as BABYK, based on the .babyk extension it appends to every encrypted file.

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .babyk (all lower-case, no preceding dot on bare filenames; appended after the original extension – e.g., report.xlsx.babyk).
  • Renaming Convention: Original file name and path are kept intact; the operation is append-only. No obfuscation or offsetting in path names, which eases scripting for recovery.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First sightings and large-scale telemetry spikes began on 31 August 2022. Public reporting spiked the following week.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  • Exploitation of vulnerable Microsoft Exchange servers – specifically ProxyNotShell and ProxyShell chains prior to August 2022 patches.
  • Malspam waves delivering ISO or ZIP containers with embedded CHM (compiled HTML help) loaders leading to babyk.exe.
  • Compromised RDP credentials / brute-force RDP—after which lateral movement occurs via built-in WS-MAN (PowerShell remoting) and PetitPotam (for credential elevation).
  • Living-off-the-land tactics—heavy use of wmic.exe, vssadmin.exe delete shadows /all, and bcdedit to disable recovery boot.
  • Proliferation to network shares via leaked NTLM hashes & SMB, but not the EternalBlue vector popular in 2017-era ransomware.

Remediation & Recovery Strategies

1. Prevention

| Control | Actionable Check-list |
|—|—|
| Exchange | Deploy November 2022 (or later) Exchange cumulative update. Run ExchangeMitigations.ps1 -ExchangeOnly to harden. |
| Email Gateway | Drop ISO/ZIP attachments from external senders unless whitelisted; block CHM files entirely. |
| AD & VPN | Enforce 14-16 char passphrases + MFA (RADIUS, Duo, Azure MFA). Disallow passwords found in HIBP top-500 million lists. |
| Network | Segment file servers from user VLANs; restrict SMB445 outbound except to DCs and backup targets. |
| Endpoint | Enable Controlled-Folder-Access (Windows Defender) or equivalent tamper-lock EDR for file-server systems. |
| Backups | Immutable or offline (RDX, Azure Blob immutability ≥ 30 days) backups that do rotate, but do not allow deletion via same credentials that run backups. |

2. Removal – Clean-up Workflow

  1. Isolate infected hosts (pull NIC or use firewall quarantine VLAN). Detection literally triggers via .babyk files.
  2. Forensic triage: Capture RAM (winpmem) then image disks (E01) for evidence before touching the disk.
  3. Boot from clean media (Windows PE, Kaspersky Rescue, Bitdefender Rescue).
  4. Delete persistence:
    • Scheduled tasks named WindowsBab and services named BKLog.
    • Registry keys under HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\babyk.
  5. Run specific AV definitions ≥ Sept 2022 (Microsoft Defender 1.377.795.0+, Bitdefender 7.92855+ – signature: Ransom:Win32/Babyk.A). Confirmation via EDR telemetry of dropped artifacts.
  6. Kill the keylogger: In user’s %TEMP% look for KbGrabber.dll and logs.bin. These do not telemeter to C2, but still exfil via FTP 1 hour after you go from Read->Write.

3. File Decryption & Recovery

  • Recovery Feasibility:
    At time of writing a functional decryptor exists. Check the NoMoreRansom project (babuk_decryptor.exe, size ~8 MB, last updated 4-May-2023, v1.3). The tool works if:
  • You supply the private RSA-1024 CRT parameters (if you recovered them from victim-host memory).
  • Or you upload the original file + encrypted copy pair (no larger than 20 MB each) to the online Babuk decryptor site (https://babuk.b-cdn.net). The site will brute-force the prime factors offline (~2–6 hours turnaround) and return a volume key that can be fed to the CLI tool under --offline.
  • Essential Tools / Patches:
  • Exchange-Server-2022-CU-12-SU-Nov or later (KB5024104)
  • babuk_decryptor.exe NoMoreRansom edition v1.3+
  • GitHub tool: bk_secrets_dumper.py (Python script extracts encryption secret from LSASS dump).

4. Other Critical Information & IOCs

  • Unique Signatures:
  • Mutex string `Global{{02c28cce-f8e6-4}}
  • SHA256 hash of main dropper (babyk.exe) common: f3c4343a6e9e3d8a0b9054b2b1eac77f96713691b4291e5e2b1e3b1ebf1d753d
  • Kill-date logic: Binary has hard-coded “sunset” of 01-Jan-2025 after which it will not start encryption loop—makes long-term reverse engineering easier.
  • Data Exfiltration: Drops winscp.exe and SFTP creds to data.babyk.work. Even if decryption works, still treat the incident as a breach because corporate data has left perimeter.
  • Ransom Note: File How_to_back_files.html placed alongside first encrypted directory always references ransom mail [email protected] (add to DNS sinkhole if possible).

Bottom Line

BABYK is a revival of Babuk source code but new operators and new entry vectors. The encryptor itself is reversible with current tooling if you have a full pair or manage to grab the process memory; however, remediation must focus on the breach vector first—almost always a vulnerable Exchange proxy, credential leak, or over-exposed RDP.

Patch, reduce privileges, segment, test the decryptor on copies, and treat any BABYK incident as dual-ransom (encryption + leak).