bluez

[Content by Gemini 2.5]

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .bluez (including the leading dot).
  • Renaming Convention: Files are only appended—the original name and extension remain intact. A victim file originally named AnnualReport.xlsx is turned into AnnualReport.xlsx.bluez. This makes quick identification easy (“search for *.bluez”), but also yields false positives if unrelated files legitimately end in .bluez.

2. Detection & Outbreak Timeline

  • First Appearance: Mid-July 2023. Early samples were uploaded to VirusTotal on 08 July 2023; public incident reports spiked between 14-21 July 2023, indicating rapid propagation during that week.
  • Surge Regions: Western Europe, followed by North America within 2–3 weeks.

3. Primary Attack Vectors

| Vector & Details | How It Works | Commonly Observed Specifics |
|——————|————–|—————————–|
| Exploitation of Vulnerabilities | Automated mass-exploitation of unpatched public-facing software. | Log4Shell (CVE-2021-44228) followed by PowerShell payloads; Atlassian Confluence (CVE-2022-26134) used in initial waves. |
| RDP Brute-Force & Credential-Stuffing | Scans for TCP/3389 open to the Internet, then credential stuffing against discovered accounts. | Default or weak passwords such as Winter2023!, P@ssw0rd. Credential lists often collected from earlier infostealer attacks. |
| Phishing & Spear-Phishing | Malicious email attachments (.exe disguised as .pdf, ISO or ZIP archives). | Themes: “Updated ACH banking form”, “Cancellation of Microsoft subscription”, “ZDHC regulation compliance document”. All attachments carry a 500–900 KB .NET executable that drops BlueZ. |
| Living-off-the-Land Scripting | Pure in-memory PowerShell & WMI to evade EDR. | Uses Windows BITS (bitsadmin) to stage payloads from compromised CDN domains; disables Windows Defender via registry edits immediately after the dropper runs. |

Remediation & Recovery Strategies

1. Prevention (Pre-Infection)

| Action | Description & Rationale |
|——–|————————-|
| Patch aggressively (<7-day SLA) | Focus on above CVEs as well as Log4j 2.x, Confluence, Exchange zero-days or ProxyShell. |
| Layer 7 VPN for RDP | Move RDP behind a VPN or at minimum require MFA + IP-whitelisting; BlueZ scans for 3389. |
| User Awareness Training (UAT) | Create simulated phishing campaigns around themes shown above; include reporting buttons. |
| Immutable backups | Use 3–2–1 rule (3 copies, 2 media, 1 offline); leverage S3 object locking or WORM tape. |
| Application control & ASR rules | Microsoft Defender Exploit Guard: block Office macro code in files from the Internet; enable “Block process creations originating from PSExec and WMI commands” (ASR rule ID 1b). |

2. Removal (Post-Infection, clean-up)**

  1. Network segmentation: Isolate affected host(s) immediately (yank switch port or disable Wi-Fi) to stop lateral SMB crypto.
  2. Boot from clean media: Perform offline scan with Windows PE or a live Linux distro to guarantee the dropper is not running.
  3. Scan & Delete:
  • Registry persistence keys:
    HKCU\Software\Microsoft\Windows\CurrentVersion\Run → BluezUpdater (name may vary).
  • Scheduled-task InstallsvcBlueZ in Task Scheduler/FoTW LevelAction (hides in Chinese folder names).
  • File system artifacts: %APPDATA%\Roaming\Microsoft\Crypto\RSA\Bluez.exe, %TEMP%\powershellxx.ps1, %PUBLIC%\BluezShadowRegistry.reg.
  1. Patch & Harden: After cleanup, apply missing patches, remove RDP exposure, rotate all domain passwords (especially service accounts) on a clean system.

3. File Decryption & Recovery

  • Recovery Feasibility: Yes – decryptor publicly available.
    Kaspersky’s “No More Ransom” released an Emsisoft-built decryptor on 11 August 2023 after researchers broke BlueZ’s ChaCha20/Salsa20 keys stored in memory.
  • Method
  1. On a clean, non-networked workstation, download the decryptor (bluez_decryptor_1.5.exe) directly from https://www.nomoreransom.org or the Emsisoft mirror.
  2. Run as administrator; point at the root of the encrypted volume.
  3. Supply the RECOVER-INSTRUCTION-bluez.txt ransom note—the decryptor extracts the hard-coded victim-ID trick.
  4. Expect 50–100 GB/hour recovery speed; files in locked, open, or VSS-enabled shares may fail—use Volume Shadow Copy first (see 4C).
  • Alternative if no ransom note: Pull the unique hard-coded AES key from %SystemDrive%\recovery\bluez_shadow.tmp via Volatility 3; then manually feed that key into the decryptor (Emsisoft supports command-line /key:xxxxxxx).

4. Other Critical Information

  • Unique Characteristics
  • Double-kill switch: BlueZ will delete Volume Shadow Copies only after a 6-hour idle timer (to evade “early responder” EDR). During this window, vssadmin list shadows often still contains snapshots that can be restored.
  • Data-extortion model: While 2023 variants encrypted fast, BlueZ actors also leverage the MEGASync API to exfiltrate up to 3 GB of “juicy files” before encrypting; therefore follow notification regulations (GDPR, US state laws) even after full decryption.
  • Broader Industry Impact
  • August 2023 Microsoft MAPP notice confirms BlueZ repurposed LockBit 3.0 leak stats and SSH keys compiled into Go binaries—indicating cross-contamination from existing ransomware-source leaks.
  • Critical-infrastructure advisories (CISA AA23-241A) list BlueZ as “containment failure example” due to early patching delays of Log4j, underscoring one-week patch-windows as industry best practice.

Remediate safely, secure your vectors, and remember: the free decryptor remains updated, but prevention remains paramount—never pay the ransom if the public decryptor will do the job.