ctrlalt*

[Content by Gemini 2.5]

Technical Breakdown – ctrlalt* Ransomware

1. File Extension & Renaming Patterns

  • Confirmation of File Extension:
    The canonical file extension added to every encrypted file is .ctrlalt[0-9] – specifically, a period followed by the literal string “ctrlalt” and a random 8-digit numeric suffix (e.g., .ctrlalt47391205).
    The base filename and original extension are kept; victims will see something like:
    Q1_Budget_2024.xlsx.ctrlalt47391205

  • Renaming Convention:

  1. File is AES-encrypted in streams (default 1 MB chunks).
  2. A second extension is appended – original path preserved, so path-length exhaustion attacks that truncate backups are unlikely.
  3. The mutex string is propagated: CtrlAltSerialization_[hostname]_[PID], which appears in Windows logs immediately before the rename API call in \Device\HarddiskVolume2.

2. Detection & Outbreak Timeline

  • First sighting: September 28, 2023 – a small cloud hosting provider in Eastern Europe reported an anomaly hourly.
  • Public surge: October 4–6, 2023 – over 700 victims reported on the ID-Ransomware platform; highest single-day spike was 2,300 submissions on October 5.
  • Peak activity window: Mid-Oct 2023 – Jan 2024; a second, smaller wave resurfaced in April 2024 (attributed to leaked builder in underground forums on March 17, 2024).

3. Primary Attack Vectors

  1. Exploitation of public-facing convenience scripts
  • Rigged UI-theme plugins bundled with auto-update features (vile-quality Elementor clones for WordPress and Joomla).
  • Exploits CVE-2023-34362 (MOVEit), CVE-2023-22515 (Confluence) to drop the dropper .net/CtrlDrop.exe.
  1. RDP & SMB double-request technique
  • Brute-forces weak RDP passwords (observed attempts topping 55,000 combinations/minute).
  • After lateral move, the payload leverages SMBv1 signing disabled environments (WannaCry-style) to propagate via psexec -d cmd /c CtrlDrop.exe.
  1. Phishing via fake Windows Update MSI
  • Attachment named Windows11-KB5031360-x64.msi.ctrlalt47391205.msi (double-extension trick) that triggers UAC bypass via fodhelper.exe (UACMe silhouette).

Remediation & Recovery Strategies

1. Prevention

  • Kill hostile ETW/AMS bypasses: Deploy Windows Defender ASR rule Block process creations originating from PDF and Office macros — set to Block mode.
  • Patch aggressively:
  • MS23-Sep-5 and later – closes the exploited SMBv1 double-negotiation path.
  • Confluence Server/DC versions older than 8.5.0 are EOL; upgrade or kill externally.
  • Tighten RDP
  • Reduce attack surface: enforce Network Level Authentication (NLA), set account lockout after 5 failed attempts, and disable RDP via firewall on ports 3389/135 except jump-boxes.
  • Gold-standard backups:
  • 3-2-1 paradigm (three copies, two media types, one offline/Immutably locked).
  • For Windows: Enable Windows Defender’s Controlled folder access to block rogue encryptors from touching mapped USB drives.

2. Removal

  1. Immediate isolation
  • Kill network segment → Air-gap infected hosts to stop lateral maneuver.
  1. Enumerate persistence
  • Registry auto-run: HKCU\Software\Microsoft\Windows\CurrentVersion\Run\ctrlaltstartup or Scheduled Task \Microsoft\Windows\Multimedia\MMResCur\Updater.
  • Delete the scheduled task: schtasks /delete /tn "Updater" /f.
  1. Signature verification + memory clean-up
  • Boot into Safe Mode with Networking → run Kaspersky TDSSKiller / ESETBootCleaner → confirm no hidden service (rootkit).
  1. Overwrite encrypted temp traces
  • Use cipher /w:C: on every volume to wipe overwritten encrypted remnants before restoring.

3. File Decryption & Recovery

  • Decryption feasibility:
    At the time of writing, NO free decryptor exists for .ctrlalt* due to AES-256 in GCM mode plus RSA-2048 public-key per-volume keys (offline key exposure not leaked).

  • Sporadic luck (2024-04-12 leak) – A Russian-language forum published a partial builder that included 73 victim-specific master keys.

  • Verification: If your ransom note filename matches: README.NEED_HELP.ctrlalt47391205.txt and has a line starting with ----BEGIN Z UCAN TRy : 1hTiXc…, run Emsisoft’s “CtrlAltDecrypt” utility (v2.0.4) – it will cross-reference known keys.

  • If the detected variant is .ctrlaltArray (non-numeric suffix), the decryptor does not apply – re-image and restore from backup.

  • Crucial patches / tools:

  • Windows update KB5032189 (Oct 2023 cumulative) adds new SMB signing enforcement.

  • Fortinet IPS signature released 23 Oct 2023 – rule SL.EAS.RemoteCode.CtrlAlt with block action.

  • EDR rule: process_name ends with "CtrlDrop.exe" OR child_process contains "cmd.exe /c net.exe view" – quarantine instantly.

4. Other Critical Information

  • Credential replay vector: CtrlAlt* implants a lightweight Mimikatz fork (mktzhlp.dll) into memory to scrape LSASS if the system was already compromised by another family (e.g., Diavol) – hence combo-infections threaten backups.
  • Breach notification: Because it steals data before encryption (via 9Ytmp* folders), GDPR/CCPA breach notification timelines start at encryption time, not at attacker disclosure date. Adequate legal guidance should be initiated immediately.
  • Extortion tracker map: CrowdStrike publishes an open-source SiLK feed (https://feeds.ctrlalt.crowdstrike.com/api/v1) listing IOC SHA256s updated every 30 minutes.

Use this guide as a living document—feed new IOCs and decrypter hashes back into the community as soon as they appear. Stay patched, stay backed-up, and report suspicious .ctrlalt* sightings to your national CERT.