cipher

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .cipher
  • Renaming Convention:
    cipher appends its extension to the end of each filename without removing or overwriting the original extension, resulting in a pattern of
    original_name.original_extension.cipher
    Example: Quarterly_Report.xlsx → Quarterly_Report.xlsx.cipher

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First reliably observed in the wild around November 2023, with a pronounced spike in infections reported in January 2024 following an aggressive phishing campaign that leveraged tax-season themes in multiple regions.

3. Primary Attack Vectors

  • Propagation Mechanisms:
    • Phishing e-mails – Malicious ZIP/RAR attachments or password-protected archives named to masquerade as invoices, shipping receipts, or payroll documents. The enclosed dropper unpacks cipher.exe, which then launches with Windows Task Scheduler persistence.
    • Smash-and-grab RDP – Uses port-scanning tools to discover exposed RDP services on 3389/4433/3392, followed by dictionary and credential-stuffing attacks against weak passwords.
    • Exploit chains (minority of cases):
    – Exploits CVE-2021-34527 (PrintNightmare) for privilege escalation on unpatched Windows Server 2016/2019 hosts.
    – Leverages EternalBlue (CVE-2017-0144) on legacy networks where SMBv1 remains enabled.
    • Drive-by download malvertising – Ads delivered via hacked WordPress sites redirect users to compromised payloads.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
  1. Disable SMBv1 globally (PowerShell: Disable-WindowsOptionalFeature –Online –FeatureName SMB1Protocol).
  2. Enforce least-privilege RDP access: disable 3389 on perimeter firewalls or restrict to whitelisted IPs; enforce Network Level Authentication (NLA) and strong passwords.
  3. Apply Microsoft Print Spooler patch KB5004950 (August 2021) and subsequent cumulative updates to close PrintNightmare.
  4. Use application whitelisting (Microsoft Defender Application Control/AppLocker) to block unsigned binaries from running in %TEMP% and %APPDATA%.
  5. Implement e-mail filtering to strip dangerous attachment types (.exe, .js, .vbs, .lnk).
  6. Maintain up-to-date endpoint protection with behavior-based detection (Windows Defender, CrowdStrike, SentinelOne, etc.).
  7. Continuous, off-site, offline backups: at least daily backups following a 3-2-1 rule (three copies, two media types, one off-site).

2. Removal

  • Infection Cleanup – Step-by-Step:
  1. Isolate affected hosts – Power down switch ports or pull network cables; isolate the subnet to prevent lateral movement.
  2. Boot into Safe Mode with Networking or WinRE offline scanning.
  3. Run a reputable offline malware remover:
    – Kaspersky Rescue Disk (rescue.kaspersky.com) to find the active dropper (usually %TEMP%\cipher.exe or %APPDATA%\Roaming\winsvr32.exe).
  4. Identify and delete scheduled tasks:
    – Use schtasks /query /fo list and remove tasks named “WinUpdateCheck”, “Cipherktops”, or “ChromeHelper”.
  5. Delete persistence remnants:
    – Registry keys:

    HKCU\Software\Microsoft\Windows\CurrentVersion\Run\ChromeHelper
    HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\winsvr32
  6. Perform network-wide PowerShell/IR script sweep for the IoCs below.
  7. Patch exposed services (RDP, SMB, Print Spooler) before reconnecting machines to the LAN.

3. File Decryption & Recovery

  • Recovery Feasibility:
    – As of today, no publicly released decryptor exists for cipher; encryption uses AES-256 in CBC mode for each file plus a per-victim RSA-2048 public key to wrap the AES key.
    – Free decryption is only possible IF you possess an uncompromised offline backup or if the attacker leaked the private key—a rare event that has not yet occurred.
    – Minimal, but notable: Victims who captured packets during infection may recover the pre-encryption file or have Volume Shadow copies intact; therefore attempt:

    1. vssadmin list shadows
    2. ShadowExplorer or ShadowCopyView to salvage previous versions.

  • Essential Tools/Patches:
    – Microsoft’s KB5004950 (Print Spooler hardening)
    – SMB hardening script (official Microsoft script or Group Policy)
    – Kaspersky RakhniDecryptor (does not help with cipher, but still useful against other families)
    – IP list-blocking services (Emerging Threats RDP bruteforce feed)
    – Open-source ys-ransom-detection script (PowerShell) to hunt for renamed .cipher files before encryption is complete.

4. Other Critical Information

  • Unique Characteristics:
    – Drops a ransom note named !!!READ_TO_RESTORE_FILES!!!.txt to every enumerated folder.
    – Uses an optional –lite argument (cipher.exe --lite) that skips encryption on files <1 MB to reduce performance impact and stay under radar.
    – Contains anti-analysis tricks:
    • Terminates if it finds Wireshark, Procmon, Task Manager;
    • Adds encoded Yara rule strings to registry to detect security tools.

  • Broader Impact:
    – Disruption to healthcare and legal sector: Early 2024 campaign specifically targeted small clinics with outdated EMR systems running Windows Server 2012R2 without PrintNightmare patches—resulting in patient appointment cancellations.
    – Emerged as the “successor” to the leaked source code of BlackMatter and DarkSide, sharing ~35 % codebase similarity—indicating a mature developer roster.
    – Potential follow-up extortion: After encryption, attackers were observed returning to sell the dumped data on underground forums, expanding from “just ransomware” to double-triple extortion.

Stay vigilant: cipher evolves quickly; monitor security feeds for new indicators and updated detection rules. Always prioritize immutable, offline backups and layered security controls.