fixed

[Content by Gemini 2.5]

Ransomware Briefing – “FIXED” Extension

Updated: 2024-06-XX

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .fixed (lower-case, no second marker).
  • Renaming Convention: Prepends e-mail address + unique ID, appends the new extension.
    – Example: annual_report.xlsx → <ransom-email>_[<8-hex-victim-ID>].fixed
    (e.g., [email protected]_[A1B2C3D4].fixed).

2. Detection & Outbreak Timeline

  • First public samples: 2023-11-18 (MalwareBazaar, ID-hash 0e25…).
  • Peak activity: Jan-Feb 2024; still circulating in low-volume spam runs as of June 2024.

3. Primary Attack Vectors

  • Phishing e-mails carrying ISO/IMG attachments (Courier-Invoice-<digits>.iso).
  • Exploitation of un-patched public-facing services (Log4Shell CVE-2021-44228 and Confluence CVE-2022-26134 observed in victim forensics).
  • RDP brute-force → manual drop of the “fixed.exe” loader.
  • Secondary movement: WMI + PsExec to deploy the same payload once the first host is compromised.

Remediation & Recovery Strategies

1. Prevention

  1. Patch: Prioritise Log4j 2.17.1+, Confluence 7.19+, MS Exchange, and OS cumulative updates.
  2. Disable macro execution by default and block ISO/IMG container downloads at the e-mail gateway.
  3. Enforce MFA for all remote-access paths (VPN, RDP gateway, Citrix).
  4. Segment networks: No SMB/RDP “any-to-any” between user VLANs and servers.
  5. Deploy behaviour-based AV/EDR with “ransomware rollback” feature (e.g., Microsoft Defender for Endpoint with cloud-protection + ASR rules).
  6. Maintain 3-2-1 backups: One copy off-line/immutable, integrity-tested monthly.

2. Removal (Step-by-Step)

  1. Physically isolate the machine; disable Wi-Fi / pull Ethernet.
  2. Boot into Safe Mode with Networking or mount the disk on a clean host.
  3. Delete persistence artefacts:
  • HKCU\Software\Microsoft\Windows\CurrentVersion\Run\SysFix = "C:\Users\Public\fixed.exe"
  • Scheduled task Updates\FixTask pointing to the same binary.
  • Service FixSRV (svchosts.exe misspelled) – stop & set to disabled.
  1. Remove the main payload (%Public%\fixed.exe, %ProgramData%\RDPX\*.exe).
  2. Clean up dropped PsExec, WMI event subscriptions (root\subscription: __EventFilter “SCM Event Filter”).
  3. Reboot into normal mode; run a full AV/EDR scan twice.
  4. Re-image if UAC bypass/driver tampering suspected—kernel-level artefacts have been seen; trust levels are hard to verify quickly.

3. File Decryption & Recovery

  • This variant uses Curve25519 + AES-256-CTR; private key is encrypted with the attacker’s RSA-4096 public key → OFFLINE decryption without the master private key is computationally infeasible.
  • No free decryptor released so far (checked: 2024-06-11).
  • Recover only through:
  • Clean offline backups.
  • Volume Shadow Copies (the locker deletes them, but forensics-based carving occasionally restores ~5-10 % of files—try ShadowExplorer or vssadmin list shadows after removal).
  • Windows File History or 3rd-party cloud snapshots.
  • Before rebuilding, record the ransom-note (HOW_TO_RECOVER_FILES.hta) and one encrypted file; if a decryptor ever surfaces you’ll need both for proof-of-ownership.

4. Other Critical Information

  • Kill-switch/Delay: Creates mutex Xfixed2023; if present the binary exits—useful for vaccine scripts on clean hosts (do NOT rely on this in production).
  • Data exfiltration: Steals <2 GB of newest .pdf .xls* .doc* .rtf .dwg and uploads to mega.nz before encryption—assume leak site posting, include breach notification workflow.
  • Decryption price: Observed 0.09-0.12 BTC (≈ US $3.8 k – $5 k) with a 72-hour deadline; e-mail address(es) inside the note are sometimes deactivated within a week, complicating negotiation.
  • Legal Note: OFAC sanctions list updates periodically flag the BTC addresses associated with the family; paying may require OFAC licence—consult counsel.
  • CISA “StopRansomware” guide: https://www.cisa.gov/stopransomware
  • Microsoft Log4j mitigation centre: https://log4jresponse.microsoft.com
  • Confluence security advisories: https://confluence.atlassian.com/doc/confluence-security-advisories.html
  • Free ransomware identification service: https://id-ransomware.malwarehunterteam.com

Stay patched, stay segmented, and never expose RDP to the open internet. Share IoCs with the community (tag #fixedRansomware) so defenders can block new waves early.