coaq

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: coaq
  • Renaming Convention:
    All affected files are appended with the .coaq extension only. The base filename remains untouched—so a file named QuarterlyReport.xlsx becomes QuarterlyReport.xlsx.coaq.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Mass-mail-distributed samples observed in mid-August 2021 and remained a top-spread campaign through Q4 2021. Surge peaks match Tuesdays/Wednesdays coordinated from the Dharma operators (= alias PHOBOS family).

3. Primary Attack Vectors

  • Propagation Mechanisms:
    • RDP brute-force & lateral RDP: Attackers scan for open TCP/3389, run credential-stuffing lists, pivot inside via RDP before manually executing the loader (1.exe, info.hta, Enc.exe).
    • Phishing mail attachments (.exe, .iso, or .zip → .scr inside) claiming to be “password-protected invoices”.
    • Exploitation still rare for Phobos class—does not use EternalBlue or other exploits explicitly; Dharma/Phobos is almost always human-driven.
    • Network shares: Mapped drives and unprotected NAS/SMB shares across a flat network are scanned and encrypted once lateral access is obtained.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
  • Disable external RDP entirely or relocate behind VPN + MFA. Change default TCP/3389 and enable NLA.
  • Enforce unique, complex AD passwords, lockout policy, and 24-hour IP block for 5 failed attempts.
  • Patch OS and third-party software regularly (esp. browsers, 7-Zip, Adobe, Office).
  • Restrict executable attachments at the mail gateway (.exe, .scr, .com, .pif).
  • Isolate legacy NAS devices into separate VLANs, block SMB/RDP on firewall.
  • Enforce application allowlisting or EDR monitoring on servers (block untrusted exes).
  • Maintain 3-2-1 backup (3 copies, 2 media, 1 offline/off-site and immutable).

2. Removal

  • Infection Cleanup (step-by-step):
  1. Disconnect affected machine(s) from the network (pull cable/wifi).
  2. Boot into Safe Mode with Networking or an offline rescue environment.
  3. Run recent AV/EDR signature offline scan (Sophos, Kaspersky, SentinelOne, Bitdefender, etc.). Vacuum all instances of Enc.exe, 1.exe, Locker.exe, and scheduled tasks (“chkntfs”).
  4. Check persistence:
    • HKCU\Software\Microsoft\Windows\CurrentVersion\Run for odd values.
    • C:\ProgramData\ for randomly-named .exe/.bat/ocx.
    • Scheduled tasks “rustagent” or “Tasks {GUID}” → delete.
  5. Run Autoruns (Sysinternals) to confirm no re-start entries remain. Reboot normally.
  6. Do not run data-restore tools on the live system; proceed to decryption section.

3. File Decryption & Recovery

  • Recovery Feasibility:
    It is NOT presently possible to decrypt files for free. coaq uses AES-256 to encrypt each file, then protects the AES key with an RSA-1024 public key unique to the victim. The matching private key remains on the attackers’ server. No flaws have been found in this implementation (as of June 2024).
  • Options:
  • Check periodically at NoMoreRansom.org archive ID 0450 or Emsisoft decryptor site; if keys are ever released (rare), a free tool will appear there first.
  • Restore from clean offline backups created before the infection date.
  • If no backups, professional negotiation is taking ~1600–16000 USD in Monero(XMR) samples; law-enforcement recommends against paying—no guarantee of working decryptor or file recovery.
  • Essential Tools/Patches:
  • Sophos Phobos/Bangkok decryptor (now only works with provided keys).
  • Windows patches: 2021-09 cumulative (KB5005033) adds CredSSP protocol fixes, but patching is still key.
  • RDP-level hardening: Configure GPO “Allow users to connect remotely…” to specific group; enforce NLA (=Win CredSSP), TLS, and require FIPS-compatible algorithms.

4. Other Critical Information

  • Unique Characteristics:
  • ~~“.coaq is just one surface extension—the strain appends additional victim IDs and campaign codes later ([[email protected]].Coaq).~~ Sticker note: ID can expose organisation’s real email, aiding forensics.
  • Drops info.hta + info.txt ransom notes in every encrypted directory—Phobos’ tell-tale double-ransom note pattern.
  • Does not delete Volume Shadow Copies but the batch script (“vssadmin delete shadows /all /quiet”) is always present post-infection—act fast if you suspect infection.
  • Broader Impact:
  • While not as flashy as Conti or LockBit, the Dharma/Phobos lineage (coaq included) has been in top-10 ransomware by incident count globally for 2022-2023. Small-to-mid-size businesses, MSPs, healthcare, and municipal offices lacking MFA or offline backups are prime targets. Chain interdiction (kill RDP spray campaigns) is considered one of the most effective ROI defenses.

Stay vigilant, keep backups offline, and close the gap on exposed RDP—coaq rarely shows up where these basics were in place.