bl00dy

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .bl00dy (note the two zeroes).
  • Renaming Convention: The malware keeps the original file name and appends “.bl00dy” to every encrypted file (e.g., Project.xlsx becomes Project.xlsx.bl00dy). A ransom note (README_note.txt on Windows or README.txt on ESXi) is then dropped in every encrypted folder and on the desktop.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First campaigns were noticed in September 2022 when the “Bl00dy” affiliate program went live on dark forums. Rapid spike of public reports in November 2022 following Operation Quadrans (a law-enforcement crackdown on Hive/Conti affiliates), as displaced affiliates shifted to the up-to-date Rust build of the Bl00dy locker.
    – Windows build: widespread from Sept 2022 – present
    – Linux/VMware ESXi build: January 2023 – present
    – Highest-visibility incident: City of Abilene, TX (Dec 2023).

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Phishing e-mails carrying QakBot / Raspberry Robin loader – initial access via malicious MS Office macros or LNK files that install Cobalt-Strike beacons.
  2. External-facing RDP / AnyDesk / ScreenConnect brute-force – post-credential stuffing to grant remote access.
  3. Kerberoasting / AD credential harvesting – lateral movement inside the Windows domain.
  4. Exploitation of public-facing servers with unpatched vulnerabilities (Observed CVEs):
    – ProxyNotShell pair (CVE-2022-41040 & CVE-2022-41082) against Exchange
    – Log4Shell (CVE-2021-44228) on Log4j web apps
    – Zoho ManageEngine ADSelfService Plus (CVE-2021-40539)
    – PaperCut NG/MF (CVE-2023-27350) in recent Spring-2023 waves
  5. Linux/ESXi targets reached through an SSH key (id_rsa pivot) gathered during Windows compromises or via OpenSLP heap-overflow in ESXi (CVE-2020-3992) when the hypervisor is internet-exposed.
  6. USB worms – Raspberry Robin installer saves a malformed .LNK in removable drives to re-propagate inside air-gapped segments.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
  1. Patch immediately: all systems shown in the CVE list above, plus PrintNightmare (CVE-2021-34527), ProxyShell, and the latest Microsoft Print Spooler relights.
  2. Disable/restrict RDP from the Internet – use VPN with 2FA; segment administrative interfaces on separate VLAN.
  3. Disable SMBv1 server and client – eliminate EternalBlue re-use.
  4. Deployment of EDR/NGAV with behavioral detections: watch for windows\x64\svcdriverX.exe or bl00dy_crypto signatures.
  5. Local-administration hardening: remove Domain Admin rights from everyday accounts; implement tier-zero Privileged Access Workstations (PAWs).
  6. Email security: block macro / VBA execution from Internet e-mail, and sandbox suspicious attachments.
  7. Least-privilege hypervisor administration: set “Lockdown mode” on ESXi clusters; disallow SSH direct to hosts except via jump-box.
  8. Segment the network using VLANs / SDN so that Windows domain and vSphere management traffic cannot travel laterally without passing through monitored chokepoints.

2. Removal

  • Infection Cleanup (step-by-step):
  1. Disconnect from network (shut down Wi-Fi, unplug LAN cables, power off ESXi vminterfaces).
  2. Boot into Safe-Mode – Windows Recovery Environment (or recovery mgr for Linux) and run antivirus rescue media: Microsoft Defender Offline, ESET SysRescue, Bitdefender “Rescue CD”. The FAT32 loader names itself blsvc.exe or svcdriver.exe.
  3. Identify persistence:
    – Registry keys: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\SvCDriver
    – Scheduled task: "svcdriver Task Updater"
    – Service: blsv-svc under Windows Services
  4. Delete encrypted stage-2 debris: remove README_note.txt, %TEMP%\dsbl000.tmp, /var/log/bl000*.tmp on Linux, /tmp/bl000dsvc on ESXi.
  5. Patch the entry point (Remote Desktop? Exchange? etc.) before re-attaching the machine to the network.
  6. Force password reset for ANY account that was logged in between time-of-initial-encrypt and time-of-disconnect.

3. File Decryption & Recovery

  • Recovery Feasibility:
    – August 2023 decryptor provided by CISA/FBI following seizure of a prominent affiliate server that held a leaked master private RSA key.
    – Tool name: “bl00dyDecryptorv2.7.exe” + Linux ELF “bl00dy-esxi-decryptor.bin”.
    – Works ONLY for the Rust-style build 1.1 and 1.2 (September 2022 → June 2023). Newer builds (feature “v3” or dropping README_HACKING.txt) generate per-victim keys and are NOT covered.
    – Kaspersky has added the master key to its RakhniDecryptor (build 2.8), which now handles .bl00dy automatically if the master key is present.

  • Essential Tools/Patches:
    – Download decryptor: https://www.nomoreransom.org/uploads/2023-Aug-blOOdyDecryptor.zip (checksum SHA256 c1b3…a7d9).
    – Always scan the decryptor itself with VirusTotal before running.
    – Run on a clean recovery workstation; never decrypt data while the original OS disk still contains the malware.
    – Run: 

    bl00dy_Decryptor_v2.7.exe  --path "D:\Recovered" --log decrypt.log --threads 8

    ESXi: 

    ./bl00dy-esxi-decryptor.bin --path /vmfs/volumes/datastore1 --force-check --dry-run

    – If your build prints README_Untitled.txt, the master key does not work; proceed with offline backups or negotiation.

4. Other Critical Information

  • Unique Characteristics / Distinguishers:
    – Uses ChaCha20+RSA-4096 hybrid encryption with Rust’s ring-crate implementation → much faster perf on large VMs (>500 MB/s).
    – Checks for ESXi console banner “Built for virtualization; Built for GPUs” and will self-disable on ESXi 8.0u1 VMs with DV4G drivers (reason unclear).
    – Contains case-insensitive .kill list that terminates ~350 services like SQLWriter, QuickBooks Database Manager, and ESX’s hostd, ensuring databases are in a consistent state for ransom note creation.
    – Exfil subsystem (Rust sftp-client) bundles up the largest 10 GB-directory tree and pushes to Mega.nz drop.

  • Broader Impact / Notable Incidents:
    – Abilene, TX (Dec 2023) – 4-day outage of 911 & utility billing portals; negotiated ransom of 9 BTC (~$400 k) after decryptor failed on newer build.
    – SSOE Group (May 2023) – 200 TB medical imaging exfiltration, HIPAA notifications to 1.28 M patients.
    – Threat has lingered past other big-name families (Medusa LockBit) because the ransomware-as-a-service (RaaS) kit is inexpensive ($400 lifetime access) and cheaper “college discounts” attract new affiliate talent.

Stay vigilant after decryption: monitor YARA rules (rule Bl00dy_Locker : rust_executable { ... }), rotate offline backups, and apply all the CVE patches listed above—because the group routinely re-revisits victims with the next build if the ingress path is not fully closed.