bowd

[Content by Gemini 2.5]

Ransomware Dossier – “Bowd” (file-extension “.bowd”)

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .bowd
  • Renaming Convention: Each encrypted file is renamed using the scheme:
    <original_filename>.<original_extension>.bowd
    Example: Project_Draft.docx → Project_Draft.docx.bowd

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First samples telemetry-collected in early April 2024. Rapid propagation waves observed during late May–June 2024 tied to large-scale phishing lures.

3. Primary Attack Vectors

  1. Malspam / Phishing
  • Themes: fake “Invoice”, “DHL Parcel Update”, “MS Teams message” PDFs attached or linked.
  • Next-stage payload is either a macro-laden Office doc or an ISO (.iso) archive.
  • Document droppers often leverage Microsoft Word Template Injection pointing to a remote DOTM hosting the bowd loader.
  1. RDP / Remote Desktop Protocol Exploits
  • Scans for TCP/3389 exposed to the internet.
  • Brute-force dictionaries + credential stuffing using previously breached credential databases.
  1. Vulnerability Exploits
  • ProxyShell (Microsoft Exchange: CVE-2021-34473, 34523, 31207).
  • Log4Shell (CVE-2021-44228) against publicly facing Java products.
  • EternalBlue (SMBv1 EternalBlue exploit / DoublePulsar backdoor) – note: recent samples embed the nsa-equation-group RDP equivalent (BlueKeep-inspired RCE) for lateral movement once inside.
  1. Supply-chain & Pirated Software Bundles
  • Cracked Photoshop, AutoCAD, and keygen torrent seeds observed distributing bowd’s downloader.

Remediation & Recovery Strategies

1. PREVENTION – Proactive Measures

  • Patch Management
  • Apply patches for ProxyShell, Log4Shell, BlueKeep MS17-010, and all Windows cumulative updates.
  • Disable SMBv1 via GPO or PowerShell: Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol.
  • Email & Web Filtering
  • Block all inbound .iso, .img, .vhd, macro-enabled Office files from external senders unless on an allow-list.
  • Configure mail-gateway rules to drop messages with suspicious TLD (.tk, .ml, etc.) attachment sources.
  • Credential Hygiene
  • Force MFA on external RDP access (Azure AD conditional access, Duo, etc.).
  • Enforce complex, unique passwords; audit for re-used passwords via HaveIBeenPwned feed.
  • Network Segmentation & Zero-Trust
  • Restrict lateral SMB/LSASS access via Windows Firewall using host-based rules:

    netsh advfirewall firewall set rule group=“File and Printer Sharing” new enable=No profile=Domain,Private
  • Application Whitelisting
  • Enable Microsoft Defender ASR rules (Block Office VBA macros from the Internet, Disable LSASS memory dumping, etc.).
  • Approve-by-policy signed code via Application Control (WDAC) or AppLocker.

2. REMOVAL – Infection Cleanup

Note: Perform this ONLY after the victim environment is completely isolated from the network (air-gapped) to avoid re-encryption.

  1. Identify and kill active bowd processes / services: 
   taskkill /f /im bowd.exe
   taskkill /f /im bowdldr.exe
  1. Disable scheduled tasks used for persistence: 
   Get-ScheduledTask -TaskName "*bowd*" | Unregister-ScheduledTask -Confirm:$false
  1. Delete bowd executed files – default locations:
  • %APPDATA%\bowd\
  • %LOCALAPPDATA%\bowd-updater\
  • Windows\System32\drivers\bowd.sys (kernel driver)
  1. Revert registry persistence:
  • HKCU\Software\Microsoft\Windows\CurrentVersion\Run → “bowdStatus” value.
  • HKLM\SYSTEM\CurrentControlSet\Services\bowdDrv.
  1. Run a reputable, fully updated security product to perform full-disk remediation (preferably offline boot).
  • Microsoft Defender Offline, Kaspersky Rescue Disk, Bitdefender Rescue CD.
  1. Ensure lateral-re-encryption rules disabled before bringing machines back online.

3. FILE DECRYPTION & RECOVERY

  • Recovery Feasibility
    – At the time of writing, NO free decryptor released for bowd.
    – Encryption algorithm: AES-256 (CBC mode) with uniquely generated 256-bit key, itself RSA-2048 encrypted using the attackers public key stored inside the binary (offline).

  • If Decryption Not Possible:

  • Restore from isolated, versioned backups (Veeam, Druva, etc.).

  • Verify backup integrity (checksums) before restore.

  • Implement 3-2-1-1 rule: 3 copies, 2 media types, 1 off-site, 1 offline/immutable.

  • Essential Tools/Patches for Prevention & Recovery

  • Patch Installer: MS17-010 (EternalBlue fix), KB5004442 (RDP hardening), KB5021131 (ProxyShell).

  • MDE “Ransomware protection” toggle & Controlled Folder Access.

  • Sysmon config to detect LSASS memory access (for Powershell Empire/downloader).

  • PowerShell logging + ELK/Splunk detection rules (keyword: bowd, entropy >7 edits/bytes).

4. OTHER CRITICAL INFORMATION

  • Unique Characteristics

  • Bowd deletes volume shadow copies (vssadmin delete shadows /all /quiet) twice: during initial encryption and again at every reboot via scheduled task, drastically reducing native recovery options.

  • Adopts “double extortion”: before encryption, bowd exfiltrates filenames/path statistics to a Mega[.]nz folder; victim receives public data-leak threat.

  • Broader Impact

  • Targeted sectors in 2024: healthcare (U.S. midwest clinics), legal/LPO (India/Philippines), and SMB regional governments.

  • Average ransom demand: 0.27 BTC (~US $10,200 at time of campaign, 2024-05-21).

  • Labour-surgical extortion group operating out of former STOP/Djvu affiliates (Russian-language underground forum xss[.]is).

  • Dark-web leak site: domain hxxps://2bowdleaks6rmcrnmd[.]onion listing non-payers with proof-of-exfiltration screenshots.

TL;DR Quick Reference Card

  • Prevent: Patch ProxyShell/Log4Shell, disable SMBv1, MFA everything.
  • Detect: Files renamed *.bowd, scheduled task “bowdStatus”.
  • Remove: Power down network, offline scan, delete tasks & registry keys.
  • Decrypt: Not feasible without official decryptor → rely on backups/offline media.