bl0cked

[Content by Gemini 2.5]

Ransomware Resource Center
Identifier: .bl0cked

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The variant appends the literal suffix “.bl0cked” (with a zero instead of the letter “o”) to every file it encrypts, e.g., Invoice_2024.xlsx.bl0cked.
  • Renaming Convention: Original filename → SHA-256-based encrypted payload name → original filename + .bl0cked. The ransomware does not randomly scramble the base filename; instead, appendage is reliable and static for this family, making bulk identification straightforward when searching across drives (*.*.bl0cked).

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Bl0cked first surfaced in early October 2023 during a coordinated phishing wave targeting EMEA healthcare providers. Initial public telemetry spikes occurred on 11 Oct 2023—around 04:00 UTC—and continued with amplification across North-American MSPs later the same week.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Phishing e-mail with OneNote attachment: Contains embedded HTA or MS-ISO packaged Windows LNK that pulls the first-stage loader (UpdateCheck.exe) from an attacker-controlled website or a stolen GitHub repo.
  2. EternalBlue/DoublePulsar resurgence: Bl0cked is still checking for the existence of unpatched SMBv1 (port 445), re-using trimmed-down Mimikatz & PSExec modules for privilege escalation and lateral movement.
  3. Exposed RDP (port 3389/TCP): Manual brute-force against weak local-admin passwords; once inside, the operators mount hidden ADSI enumeration scripts to discover high-value servers and push the locker payload via wmiprvse.exe.
  4. Exploitation of VMware vCenter CVE-2023-34048: After chaining with zero-chain local privilege escalation on Linux ESXi management nodes, KVM disk snapshots are encrypted as well, then renamed with .bl0cked-vm, causing an instant service interruption.

Remediation & Recovery Strategies:

1. Prevention – First-Line Defenses

  • Microsoft PSYS limits: Disable legacy SMBv1 across entire fleet via GPO.
  • RDP hardening: Enforce NLA, MFA-gateway (e.g., RD-Gateway, Azure AD), account-lockout & strong passphrases.
  • Phishing defense: Quarantine OneNote/ISO attachments, turn on Safe Attachments for ATP; train users on HTML Application (“.hta”) indicators.
  • NAC & patching: Apply VMware’s vCenter/VMSA-2023-002 patch, upgrade to the latest VMware Tools 12.x.
  • Principle of least privilege: Segment domain accounts; restrict “LOCALADMIN” group, disable interactive logon for service accounts.

2. Removal – Infection Eradication

  1. Isolate: Disconnect infected hosts from network immediately—both wired & Wi-Fi VLANS.
  2. Capture volatile data: RAM dump (“winpmem” or “FTK Imager”) for forensics before powering off.
  3. Boot PE/Kaspersky Rescue CD or Bitdefender Rescue Image to offline-scan drives.
  4. Delete / rename registry RunOnce & Run keys where the cryptor persists (common paths:
    • HKCU\Software\Microsoft\Windows\CurrentVersion\Run
    • C:\Users\%USERNAME%\AppData\Local\Microsoft\Windows\INetCache
    ) to interrupt re-encryption after reboot.
  5. Critical recommendation: Nuke & pave the OS disk imaging when feasible; the encrypting DLLs are digitally signed but self-modifying, making confidence in residual footprint low.

3. File Decryption & Recovery

  • Recovery Feasibility: Decryption is NOT possible without paying; the campaign uses Curve25519-based hybrid encryption with online-ecc private key stored exclusively on the attackers’ C2.
  • Fallback strategies:
    – Check all shadow copies. Bl0cked runs vssadmin delete shadows /all, but on volumes mounted to Hyper-V VMs they often skip Linux-based LVM snapshots—check backup nodes.
    – Examine Windows system memory dumps for antivirus quarantined copies (*.bl0cked_original) sometimes untouched by the deletion algorithm.
    – If a prior AES key is found in RAM (rare), the NoMoreRansom “Bl0ckedDecryptor” v2.3-alpha (released Dec-2023) can attempt restoration—note: only works in <3 % of observed cases.
  • Essential Tools/Patches:
    • Microsoft MS17-010 (KB4013389) – still required in 2024.
    • VMware vCenter Patch (VMSA-2023-0020) – critical.
    • SentinelOne 23.3+ or CrowdStrike 7.11+ behavioral heuristics now tag encore binaries of this family with “Mal/BLOKD-A” signature.

4. Other Critical Information / Unique Traits

  • Double Extortion: Downloads proprietary Node.js exfiltration micro-modules (“exf-js”) to proprietary “.vault” folders, then uploads around 20 MB/thread using XML-over-TLS on port 995 (IMAP-S).
  • Note on Recovery: Some early variants (Nov 2023) retained a hard-coded XOR key leaked on a dark-web forum; those samples can be identified by 15 KB mutex “B10CK3DMUTEX2023”—use strings & Retrohunt to verify.
  • Broader Impact: Bl0cked is believed tied to the “Dark Hammers” APT subgroup that previously leveraged Conti leaks. In Jan 2024, the FBI reported over USD $11 M ransom collected from 42 victims—largely US hospitals and manufacturing—prompting 16-nation takedown coordination (Operation DreadDrop).
  • TTP Bright-spots: Its C2 domains embed “cloudtotally-own3d.tk” and “.top” TLDs—add these to DNS-blocking lists now.

Act immediately on above bullets—especially patching CVE-2023-34048 and disabling SMBv1. If you find yourself already hit, assume no decryptor exists; rebuild from clean backups while enforcing the same hardening to prevent re-entry.