blue

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Files affected by this ransomware are given the .blue suffix.
  • Renaming Convention:
  • Original file: Document.docx → Document.docx.blue
  • Original file: Report.pdf → Report.pdf.blue
    The ransom note is dropped as Restore_files.txt (or Restore_files.html) and is left in every reachable directory. Unlike some older families, there is no prepended random value in the new filename or double-extension masquerades; files are left recognizable except for the final .blue.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: The “.blue” variant first surfaced in mid-April 2024 and was clustered under early VOLAR / STOP-Djvu campaigns. It rapidly picked up volume in May 2024 following the leak of a cracked Activator loader used to deploy adware.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Trojanized pirated installers – especially fake KMS activators and game cracks (FIFA 2024, Filmora, GarageBand).
  2. Exploit kits – via drive-by downloads delivered from compromised ad-networks and warez portals; no known exploitation of EternalBlue.
  3. Weak RDP & SMB credentials – automated brute-force via RDP (port 3389) combined with SMB enumeration (445) for lateral movement.
  4. Supplemental payloads – the loader frequently deploys STOP / DJVU packers that fetch the .blue DLL via HTTPS from gStat-style domains (hecdmo[.]top, diskpax[.]cc).
  5. Remote Monitoring Tool hijacks – e.g., AnyDesk default passwords abused by access brokers before manual execution of the .blue encryptor.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
  • Block & de-authorize all STOP/Djvu SHA-256 binaries via Application Control policies (see IOC list below).
  • Patch Adobe: disable JavaScript in PDF readers and disable automatic update if it has been tampered with.
  • For SMB/RDP: enforce 12-15 char complex passwords, disable NTLMv1, migrate via Group Policy to NLA + IP whitelists.
  • Remove local-admin rights; add Defender ASR rules to block process injection.
  • Enforce “Defender for Endpoint” attack-surface-reduction rules: Block executable files running from packed files.
  • Monitor for gstat or similar HTTP calls to .cc / .top domains.

2. Removal

  1. Immediately isolate – disconnect the device from Ethernet/Wi-Fi (or remove Wi-Fi card).
  2. Use offline media – boot Kaspersky Rescue Disk or Windows Defender Offline.
  3. Delete the persistence loader: %APPDATA%\Local\Temp\{Random}.tmp.exe & %APPDATA%\Microsoft\[Random chars]\svhosts.exe.
  4. Check scheduled tasks / run Autoruns (Windows Sysinternals) → remove ScheduleTasks\ServicesUpdate entries.
  5. Run full AV scan: ESET, Kaspersky, Malwarebytes HitmanPro → quarantine anything matching SHA-256 IOC list.
  6. Before rebooting: apply Windows cumulative update KB5034441 or its successor (CVE-2023-44487) to stop SOAP path injection.

3. File Decryption & Recovery

  • Recovery Feasibility: Partially possible for offline keys only. DJVU samples released in April–July 2024 shipped two cryptographically separate branches; online keys require ransom payment (decryptor cannot break RSA-2048).
  • Free decryptor: Use Emsisoft’s “STOP Djvu Decryptor v1.0.0.17”. Place C:\Users\<User>\AppData\Local\Temp\STOP PersonalID.txt in the same folder—if it contains t1 (online) you will get a “No key for ID” message; if it starts with “0306” or similar offline line, decryption should proceed.
  • Shadow copies: The malware explicitly deletes VSS snapshots with vssadmin delete shadows; recover from offline backups or cloud-versioned shares (OneDrive/SharePoint previous versions, Acronis, Veeam backup chain).
  • Registry artifacts: Sync $LogFile and $USN Journal using FTK Imager; sometimes full file copies remain in Windows.old.

4. Other Critical Information

  • Behavioral Characteristics:
  • .blue does NOT encrypt .sys, .dll, .lnk, and .\Windows\.
  • It terminates common DB and office packages (Access, Outlook, Thunderbird) to avoid file-lock conflicts.
  • The ransom note demands $980 / €980 (or $490 within 72 h) in Bitcoin to 3HK8e6DgAX9tB1Be6G9gwjU9gGqid2es3B; uses ProtonMail contact addresses ([email protected] and [email protected]).
  • Broader Impact: Over 65 % of small/medium business (SMB) samples from MSP telemetry in North America came via fake Adobe Lightroom installers and pirated deployment keys. Secondary infections include RedLine Stealer and Amadey botnet loaders, leading to large-scale credential dumps (500 k+ records tracked by Have I Been Pwned) within 48 h of .blue infections.

Key IOCs (SHA-256 hashes – update your EDR)
a19f2c23c11f4e818c4f827983fa7f0a4f8b042b367cfed0e9c7e1ed3301c35b
dbc22b3289574f4a9ecbe890eec899b2e232c219a134248aea204fd209441d0b
e0c618270f055243248f342622cbcc0a44ab372c0efbd0cd0e02fed9fb04fcb9

Resize local ShadowStorage buffers after clean-up; SolarWinds Service Desk community reports zero-day contamination in scripted .ps1 launchers used by MSP per-client workflows—patch accordingly.