BAVACAI Ransomware

THREAT ACTOR DESCRIPTION

BAVACAI is a ransomware variant belonging to the MedusaLocker ransomware family, identified through examination of a malware sample submitted to a malware analysis platform. It was confirmed as part of this family by five independent antivirus vendors.  

BAVACAI encrypts files on the victim's systems and exfiltrates data from the network, then demands a ransom in exchange for decryption and to prevent publication of the stolen data. The ransom note (WHATS_HAPPEND.txt) states that exfiltrated data will be published within 72 hours unless the victim makes contact.

Analysis of the BAVACAI malware sample identifies exposed RDP services exploited via brute force against weak or reused credentials as the primary known attack vector for this ransomware family

TACTICS, TECHNIQUES, AND PROCEDURES (TTPs)

Attribution Framework

All TTPs in this section use one of two status labels: CONFIRMED: Directly evidenced from BAVACAI malware sample analysis or from BAVACAI-specific ransomware tracking data. ATTRIBUTED: Sourced from threat intelligence reporting on BARADAI, a MedusaLocker-family variant confirmed to share the same Data Leak Site and operator infrastructure as BAVACAI. These TTPs are attributed to the same operator cluster with moderate confidence and have not been independently confirmed from BAVACAI binary analysis.

Phase 1 - Initial Access: RDP brute force on exposed endpoints with weak/reused credentials (T1190) or phishing/malicious attachments (T1566). Pre-obtained infostealer credentials also used (T1078; 58.3% co-infection rate).

Phase 2 - Execution & Discovery: cmd.exe orchestrates infection workflow. System, file, registry, and software discovery profiles the victim environment. Application window discovery identifies processes requiring termination

Phase 3 - Privilege Escalation: Parent PID spoofing (T1134.004) directly confirmed]. Process injection (T1055) and access token manipulation (T1134) attributed from related operator cluster analysis.  

Phase 4 - Persistence: Registry Run Key persistence (CurrentVersion\Run) attributed. HKLM\SOFTWARE\PAIDMEMES\{PUBLIC,PRIVATE} is a directly confirmed BAVACAI registry IOC.

Phase 5 - Defence Evasion: Binary packing, sandbox detection, hidden window execution, rootkit, file permission modification, and indicator removal collectively defeat endpoint security controls.  

Phase 6 - Pre-Encryption Service Disruption: taskkill/net stop commands terminate SQL Server and enterprise services to release file locks. Windows Restart Manager API used to unlock additional files.  

Phase 7 - Data Exfiltration: Victim data exfiltrated to attacker-controlled Tor fileserver before local encryption begins. 72-hour countdown to DLS publication communicated to victim on first contact.

Phase 8 - Encryption & Ransom Note: .BAVACAI extension appended. WHATS_HAPPEND.txt dropped. Victim contacted via nhuvgh@outlook.com and Tox. Encryption algorithm not specified in available BAVACAI-specific analysis.

Phase 9 - Anti-Forensics: Temporary files, scripts, and forensic artifacts deleted post-execution.

The following Sigma rule was published in threat intelligence reporting on BARADAI and is attributed to the shared BAVACAI/BARADAI operator cluster. It targets process injection activity via the Windows Sysnative folder (T1055 - Privilege Escalation).

MITIGATION - CRYSTAL EYE 5.5 CONTROLS

• Block or strictly restrict inbound RDP (TCP 3389) via CE Advanced Firewall Zone rules to authorised management IPs only.
• 58.3% of Bavacai victims had prior infostealer domain compromise [2]. CESOC dark web monitoring should actively track managed client domain credential exposure.
• CE MDR endpoint telemetry detects parent PID spoofing anomalies. Escalate immediately to CESOC on detection.
• CE IDPS rules should alert on taskkill.exe or net.exe commands targeting SQL Server services (MSSQL*, SQLAgent, SQLBrowser) outside approved maintenance windows.
• CE ForceField and CE MDR provide behavioural ransomware blocking - mass file rename events and .BAVACAI extension creation trigger immediate alerts.

INDICATORS OF COMPROMISE (IOCs)

All IOCs below are sourced from and validated against the referenced intelligence sources indicates direct evidence from BAVACAI-specific malware analysis or ransomware tracking data. ATTRIBUTED indicates evidence from the related BARADAI operator cluster.

File Hash

Network / Operator Contact Indicators

Host-Based Indicators (Confirmed - BAVACAI-Specific)

Host-Based Indicators (Attributed - Related Operator Cluster)

AV Detection Names (Confirmed - VirusTotal, BAVACAI SHA256)