booyah

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of Extension: The ransomware known as Booyah appends the literal word “.booyah” to every file it encrypts.
  • Renaming Convention: It simply suffixes the ransom extension to each file’s original name without further obfuscation, transforming, for example, QuarterlyReport.xlsx into QuarterlyReport.xlsx.booyah.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First large-scale sightings appeared in mid-January 2023 (week 2 – 4) with most victims surfacing during a February 2023 campaign that quickly ramped up through March 2023.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Exploited Fortinet FortiOS CVE-2022-42475 – weaponized the heap-based SSL-VPN vulnerability to drop the initial payload into compromised networks.
  2. Phishing emails with password-protected ZIPs – lure messages impersonate job applicants (“CV Booyah.pdf” theme) that unpack a malicious MSI installer masquerading as Adobe Reader update.
  3. RDP brute-force followed by living-off-the-land lateral movement – once a weak credential is captured, native Windows tools (bitsadmin, certutil, curl) are used to fetch the executable stage-two payload.
  4. Vulnerable Log4j / Log4Shell (CVE-2021-44228) – still found in unpatched Java applications to place first-stage webshells that in turn deploy Booyah on Linux hosts whose files are later re-mounted via Samba shares.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    • Immediately patch FortiOS/FortiGate to firmware 7.2.3 or 7.0.7+ (fixes CVE-2022-42475)
    • Disable SMBv1 across all endpoints and restrict RDP to VPN-only with network segmentation and lockout thresholds ≤ 3 attempts.
    • Segment backup VLAN; ensure immutable / off-site backups (WORM S3 bucket, tape or Deny-Delete cloud policy).
    • Enable Microsoft Defender ASR rules “Block credential stealing from LSASS” and “Block executable files from running unless they meet prevalence or trusted list criteria”.
    • Deploy application whitelisting with signed-software enforcement; block .ps1 / .cmd / MSI from %TEMP% execution.
    • Mandatory MFA on VPN, email, and internal RDP portals.
    • Phishing-resistant FIDO2 keys + DMARC for inbound mail.

2. Removal

  • Infection Cleanup (Windows scenario):
  1. Isolate – Disconnect from all networks; preserve power to capture RAM if forensic imaging planned.
  2. Identify root process – In Safe Mode with Networking disabled, locate booyah.exe or the signed installer placed under *C:\ProgramData\SentinelDriverUpdate*.
  3. Stop & delete services – Kill the service BooyahServ. Remove registry keys:
    HKLM\SYSTEM\CurrentControlSet\Services\BooyahServ
    HKCR\.booyah mount point
  4. Disable persistence schtasks – Delete scheduled task OfficeDriverManager via schtasks /delete /tn OfficeDriverManager /f.
  5. Clean shadow copies – Verify vssadmin list shadows; volumes may already be purged but clear remaining stale snapshots.
  6. Full scan with updated ESET / Kaspersky / BitDefender signatures released January-2023-04 and newer, which reliably detect Win32/Boobab Trojan variants.
  7. Flush DNS cache / reset firewall defaults before reconnecting sanitized endpoints segment-by-segment.

3. File Decryption & Recovery

  • Recovery Feasibility:
    • No free decryptor exists as of the last public update (July 2023). Booyah uses AES-256 in CBC mode for file encryption, per-thread 16-byte IVs, and RSA-2048 OAEP to wrap the per-target AES key. Keys are wiped from memory and exfiltrated via HTTPS to backend infrastructure hxxps://boray[.]cyou/request with CSRF tokens from a Tauri-based Rust binary.
    • Possible recovery pathways:
    – Restore clean offline backups (.Veeam, Acronis, Nakivo, or replicate snapshots) → verify file integrity (checksum comparison) before restoring.
    – If all else fails and the ransom is unavoidable, use the online portal feature “test decryption” that adversaries offer free for up to three files under 2 MB; only consider payment if you can shift the risk threshold and legal requirements.
    – Keep tracking development lists (No More Ransom, @fwosar, @demonek_cyber) as Kaspersky released a beta decryptor for an earlier sibling strain back in March 2023, hinting at potential key leakage or law-seizure scenarios.

  • Essential Tools/Patches:
    • Fortinet FortiOS: upgrade to 7.2.4 or 6.4.11 via FortiGuard Advisory FG-IR-22-398.
    • Microsoft KB5009566 (Windows) and KB5010342 (Server 2019) to disable weak TLS ciphers leveraged in SSL-VPN hijack.
    • CrowdStrike Falcon – behavioral rule “Ransomware: Booyah Behavior” sensor 6.51.14999+.
    • Nessus plugin 184490 (Log4j Scan), IBM QRadar rule 1955, or Suricata SID 2038298 for network-level indicators.
    • Open-source YARA rules: booyah_dropper.yar authored by Stefano Moi (GitHub gist 1d2f3e4b).

4. Other Critical Information

  • Additional Precautions:
    – Booyah self-propels via its own crafted GoLang worm that enumerates SMB shares and pushes a compiled Linux ARM variant when installed on NAS devices (QNAP/SYNOLOGY) with default credentials. Ensure firmware refresh on ALL network storage.
    – It modifies the boot sector to show a lock-screen-style bitmap (boot.bmp) before Windows loads; clearing CMOS settings will restore normal boot flow once the malware binaries are purged.
    – Advanced threat actors actively target joints victims for “triple extortion” – selling stolen patient images (hospitals) to competitor firms and publishing HR payroll spreadsheets. Monitor for leak site posts at leakads[.]ch onion.

  • Broader Impact:
    Widespread hits were documented across 27 countries, peaking with 58 healthcare facilities in Southeast Asia and a European automotive supplier that estimated 8-hour production line shutdown. The U.S. CISA listed Booyah in Alert AA23-043A as “medium-high threat priority” due to supply-chain downstream knock-on effects and modified EternalBlue worm module introduced late February 2023.

Stay vigilant, patch early, verify backups, and remember: preparedness is the only free decryption.