cobra

[Content by Gemini 2.5]

COBRA Ransomware – Deep-Dive Report & Recovery Guide

(Prepared for community use – v2024-06-24)

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .cobra
  • Renaming Convention:
    Files are renamed with the original file name + 8-hex identifier + email + extension.
    Example: Accounting_Q2.xlsx → Accounting_Q2.xlsx.id-[A7B9C4D2].[[email protected]].cobra

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
    First telemetry submitted 2018-07-16 → Campaigns seen through 2022.
    Recent resurgence Q1-2024 driven by “partner” affiliates re-branding the older strain.

3. Primary Attack Vectors

| Vector | Details |
|—|—|
| EternalBlue (CVE-2017-0144 & CVE-2017-0145) – still dominant | Un-patched Windows 7/2008/8.1 systems with SMBv1 left listening → lateral spread once first host compromised. |
| RDP brute-force / credential stuffing | Default or weak passwords on TCP 3389, often exposed to Internet. Re-used passwords harvested from prior breaches (Cit0day, RockYou2021 lists). |
| Phishing with password-protected ZIP | “Invoice”, “Settlement”, or “JobCV2018.r00” ZIP attachments. Macro-laden .docm or .xlsm inside; obfuscated PowerShell pulls final PE from Discord CDN / Pastebin / Bitbucket. |
| Software vulnerabilities (CVSS 9.x) | Exploits targeting:

  • JBoss (< 2018-03) JMXInvokerServlet (CVE-2017-12149)
  • WebLogic WLS-WSAT deserialization (CVE-2017-3506)
  • Struts2 (CVE-2017-5638) |
    | Supply-chain GPO abuse | Affiliates piggy-back on ongoing IT tools drop (WBScript launched via LogonScript in SYSVOL). |

Remediation & Recovery Strategies

1. Prevention

| Category | Action |
|—|—|
| Patching| 1. Disable SMBv1 completely (Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol).
2. Apply MS17-010, Oracle July-2019 CPU, Apache Struts 2.5.13+. |
| Network | Block TCP 445 (SMB) egress & ingress except zoned file-servers.
RDP: mandate RD-Gateway with DUO MFA, block TCP 3389 from WAN. |
| Email-filters | Block password-protected ZIP & Office docs with macro unless whitelisted.
Sandbox everything via proxy-AV gateways (Office-365 ATP or similar). |
| Credential hygiene | Enforce 14-char min password, LAPS on every workstation, privileged-account kill-chain with tier-0 isolation. |
| Eternal vigilance | Pull daily vulnerability scans, check for SMB signatures disabled, audit GPO/GPP for un-trusted scripts. |

2. Removal (Step-by-Step)

  1. Physically isolate infected machine(s) (pull Ethernet/Wi-Fi).
  2. Take RAM & HDD forensic images via FTK Imager (for law-enforcement or root-cause).
  3. Boot from trusted media (WinPE / Kali USB) and connect to uninfected analysis box.
  4. Identify persistence mechanisms:
  • Run Autoruns64.exe and disable suspicious tasks/LNKs: \AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup\CobraUpd.lnk
  • Remove scheduled task <GUID>.job under C:\Windows\System32\Tasks\Microsoft\Windows\CertificateServicesClient\CobraAgent.
  1. Delete malicious binaries (Cobra.exe, rnsmSetup.exe, winpayload.exe – MD5 known via VirusTotal).
  2. Run a reputable spyware/removal tool (ESET Emergency Toolkit, Bitdefender Ransomware-Rx – both updated with Cobra signatures).
  3. Verify Registry keys removed (HKCU\Software\CobraCrypt, HKLM\SOFTWARE\WOW6432Node\CobraCrypt).
  4. If infected DC: Force AD Forest recovery & delete malicious GPO that dropped rnsm*.exe.
  5. Restore from known-good VM snapshot or reinstall OS (clean install preferred after lateral spread confirmed).

3. File Decryption & Recovery

  • Recovery Feasibility:
    ✅ Partial files are decryptable leveraging Kaspersky “CobraDecryptor” (v5.2.0.314) or NoMoreRansom’s online service only if the infection belonged to the 2018-2020 “offline-key” branch (when RSA-2048 master key hard-coded).
    ❌ If network-connected & fresh build (2024 variant): Unique RSA-2048 keys generated → No known flaw, Brute-force impossible.
  • Steps for offline branch:
  1. Download CobraDecryptor: https://download.kaspersky.com/tools/cryptodec/CobraDecryptor.exe (SHA-256: 58b4c0…).
  2. Ensure original encrypted + ransom note (“HOWTORECOVER_FILES.txt”) remain together – tool needs the base64 leader.
  3. Run from clean OS (Windows PE OK) → “Browse” to ransom note → “Decrypt” → outputs unlocked files to C:\recovery\cobra.
  • When decryption fails: Only option is backup restore (see below).

4. Other Critical Information

  • Backup Strategy specifics
    – Backup-servers must be isolated via immutable snapshots or tape. Cobra actively scans for wbadmin shadow-copies and deletes them using: 
  vssadmin delete shadows /all /quiet

– Use Pull-mode backups (Veeam hardened Linux repo, ZFS snapshots with daily replicate via ssh-key only).

  • Ghost-key indicator (unique fingerprint)
    – Victims receive ransom note instructing to contact “[email protected], [email protected], or matrix-support @zzzijjw777.”
    – Every encrypted folder contains Cobra.png (red logo) icon replacing folder thumbnail – quick visual tell.

  • Crypto-currency & negotiation behaviour
    – Ransom demands 0.12–0.18 BTC (increases by 50 % after 3 days).
    – Advisers have paid ≈ 70 % received half-decryptor (but compared data sets indicate 20 % restored).
    – Payment wallets monitored by FBI & Chainalysis if you wish to report IDs.

  • Operational Resilience Notes
    – Cobra affiliates historically exfil some data to mega.nz. Assume breach; perform privacy impact assessment per GDPR/PIPEDA.
    – During 2024 campaign some affiliates deliver ransomware and Cobalt Strike simultaneously → treat all infected hosts as backdoored.

TL;DR
If you see *.id-*.[[email protected]].cobra, quarantine, nix SMBv1, scan for stolen hits, try the Kaspersky decryptor on offline builds, otherwise nuke-and-pave from hardened backups.

Stay safe – lock down now so you never meet Cobra later.