blower

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .blower (exact extension appended to every encrypted file).
  • Renaming Convention:
    – Victim files keep their original name plus a randomized 5-character hexadecimal ID string after the base filename.
    Example: Quarterly_Report.xlsx → Quarterly_Report.xlsx.id-A1B2C.[[email protected]].blower
    – The square-bracketed portion contains the attacker-controlled e-mail address for contact (sometimes exchanged in later variants, but usually [[email protected]]).

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Early April 2020. A noticeable spike in submissions occurred in the latter half of May 2020, coinciding with COVID-19 phishing lures.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Malspam (Phishing) – E-mail campaign using fake invoices, pandemic updates, and purchase orders with malicious .zip or .ISO attachments (droppers such as database7652.zip).
  2. Exploited RDP – Brute-force or previously purchased credential sets used to log into externally exposed Windows Remote Desktop Services. Once inside, attackers manually deploy the payload.
  3. Living-off-the-land techniques – Uses wmic.exe, powershell.exe, and vssadmin delete shadows /all /quiet to disable system protection and delete shadow copies.
  4. Missing Microsoft patches – Especially targeting unpatched Windows 7 / Server 2008 systems; however, no evidence it relies on EternalBlue. The destructive SMB propagation found in WannaCry is not exhibited by Blower.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    – Patch Windows systems immediately (all security cumulative patches since March 2020).
    – Disable RDP on internet-facing interfaces or enforce strict IP allow-listing, multi-factor authentication, and RDP Network Level Authentication (NLA).
    – Use e-mail filtering rules to quarantine archives containing .exe, .js, .vbs, .ps1, .hta attachments.
    – Deploy AppLocker/MS Defender ASR rules to block execution from %TEMP%, C:\Users\Public, or C:\Perflogs.
    – Ensure controlled folder access (CFA) in Microsoft Defender Exclusions is enabled and that important shares are under protection.
    – Segment networks and restrict lateral movement via Windows firewall local policy or microsegmentation.

2. Removal

  1. Physically disconnect the host from LAN/Wi-Fi to stop encryption processes on mapped drives and ransomware beaconing.
  2. Boot into Safe Mode with Networking or use a clean Windows RE disk; attach the infected drive to a clean workstation if possible (recommended).
  3. Run an offline scan with an updated security product or use the Emsisoft Emergency Kit, Malwarebytes, or MS Defender Offline.
  4. Delete persistence artifacts:
  • Registry: HKCU\Software\Microsoft\Windows\CurrentVersion\Run entry with randomized name pointing to %APPDATA%\{random}\{random}.exe.
  • Scheduled tasks named Update, WinUpdate, or similar in Task Scheduler Library → Microsoft → Windows → UpdateOrchestrator.
  1. Clean %APPDATA%\<random> and all sub-folders; rename rather than delete initially in case forensic snapshots are needed later.
  2. Re-image the computer if corporate policy allows; alternatively perform a fresh Windows installation after securing the shadow volume backups from an uninfected location.

3. File Decryption & Recovery

  • Recovery Feasibility:
    – No free decryptor exists for Blower 1.x–2.x as of June 2024. The strain uses secure ChaCha20 + ECDH (Curve25519) encryption.
    – DO NOT pay the ransom – custody of Bitcoin wallets is often abandoned even after payment.
    – Options:
    1. Check existing backups offline (NAS disconnected, cloud object lock).
    2. File carving with Photorec/Recuva if the original HDD/SSD has not been overwritten.
    3. Monitor the NoMoreRansom project; occasionally, law enforcement takedowns expose master keys. (Subscribe to their RSS feed for Blower-specific advisories.)
    4. Upload one ciphertext file to ID-Ransomware to confirm variant just in case it proves to be a mis-typed extension rather than true Blower.
  • Essential Tools/Patches:
    – Windows Defender update definition package ≥ May 12 2020 (definitions version 1.319.588.0 or higher).
    – KB4550965 (Server 2008 R2), KB4550964 (Win 7) – patch the exploited CVE-2020-1048 Print Spooler privilege-escalation vector.
    – Open-source RDP Shield (open-source PowerShell script) to brute-force-throttle failed login attempts.

4. Other Critical Information

  • Unique Characteristics:
    – Multilingual ransom note (RESTORE_FILES_INFO.txt) available in English, Turkish, French, German, Spanish.
    – Deletes Volume Shadow Copies and additionally clears WinRM logs (wevtutil cl) to impede traditional DFIR timeline reconstruction.
    – Poses as the Dharma/CrySIS ransomware e-mail format but is built on Phobos – independent fork.
    – Impact on hospitals and small municipalities during COVID-19 surge received notable coverage in June 2020.

  • Broader Impact:
    – Generally targeted but opportunistic; actors scan for open RDP/3389 over weeks before manual deployment—hence extended dwell time (days → weeks) prior to detonation.
    – Despite smaller ransom demands (~0.33–0.66 BTC ≈ US $4K–$8K over time), the aggregate financial impact is compounded by downtime and reputation loss for SMEs without offline backups.