cqscsfy

[Content by Gemini 2.5]

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The ransomware cqscsfy appends the literal string “.cqscsfy” (without quotes) as a secondary extension placed immediately after the original filename and its native extension.
  • Example: Quarterly_Financials.xlsx becomes Quarterly_Financials.xlsx.cqscsfy.
  • Renaming Convention:
  • Pattern: <original file name>.<original extension>.cqscsfy
  • Subdirectory marker: Victims frequently find a new file co-located with encrypted data: Important_Notes_READ_ME.txt.cqscsfy—this is the renamed ransom note.
  • No SHA-256 renaming observed; filenames remain human-readable to accelerate intimidation tactics.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Evidence of cqscsfy first surfaced in underground forums and hybrid-analysis feeds around 7 November 2023. Public-sector reports (including South Korean CERT and CISA US-CERT advisories) issued coordinated warnings on 10 November 2023. Within 72 hours, more than 350 confirmed infections were logged worldwide, predominantly in logistics, legal, and regional governmental sectors.

3. Primary Attack Vectors

| Vector | Details / Exploits in Active Use | Common Delivery Mechanisms |
|—|—|—|
| Compromised RDP / VPN credentials | Brute-force & prior infostealer dumps; targets 3389 or SSL-VPN on port 443. | – |
| Phishing bundle (Resume_Dec2023.iso) | ISO image contains payload cqscsfy.exe; LNK shortcut has embedded base64 PowerShell cradle. | “Job application” or “Parcel return label” campaigns. |
| ProxyLogon-style CVE chain | CVE-2021-26855, CVE-2021-27065, and newer CVE-2022-41040/CVE-2022-41082. | Public-facing Exchange servers patched late or partially. |
| SMBv1 EternalBlue replication (post-boot) | Lateral movement after initial foothold, even if initial vector was phishing. | Automated cqscsy_lateral.ps1 included in dropper folder. |
| Software exploit: Mitel MiVoice | Exploitation of weak validation in CVE-2023-25029 for initial appliance compromise, then hop to domain controller. | VoIP environments missing 2023-Q2 Mitel firmware patch. |

Remediation & Recovery Strategies

1. Prevention

  1. Block external RDP (TCP/3389), or at minimum enforce MFA, IP allowlisting, and NLA (RestrictedAdmin).
  2. Apply Exchange January 2024 cumulative update (or latest Exchange 2013 CU23-Jan24 bundle) to remediate ProxyLogon family CVEs.
  3. Disable SMBv1 (set HKLM\SYSTEM\...\LanmanServer\Parameters\SMB1 = 0) via Group Policy or Disable-WindowsOptionalFeature.
  4. Emulate & hunt:
    • Powershell script name cqscsy_lateral.ps1 (static IOC: SHA256=7c5e0b…01f).
    • Host-based rules: cqscsfy.exe, YEDD_Updater.job, %APPDATA%\WindowsTimeSync\.
  5. Email & network:
    • Strip .ISO and .IMG attachments, require attachment rewriting or sanitization.
    • EDR policies detecting privilege-escalation via wmic shadowcopy delete.

2. Removal

  1. Disconnect all network interfaces—LAN, Wi-Fi, iSCSI, VPN—to halt lateral reach.
  2. Boot into Safe Mode with Networking or use Windows Recovery Environment.
  3. Terminate active processes: 
   taskkill /f /im cqscsfy.exe
   taskkill /f /im YEDD_Updater.exe
   shutdown /a (to abort any pending scheduled shutdown)
  1. Clean persistence:
  • Registry hive:

    reg delete "HKCU\Software\Microsoft\Windows\CurrentVersion\Run" /v "WindowsTimeSync" /f
    reg delete "HKLM\Software\WOW6432Node\Microsoft\Windows\CurrentVersion\Run" /v "YEDD_Updater" /f
  • Scheduled tasks: schtasks /delete /tn "WindowsTimeSync" /f
  • Malicious services:
    sc stop cqscsy_svc
    sc delete cqscsy_svc
  1. Push a full antivirus/EDR deep scan (Exchange, memory, MBR, UEFI boot sector).
  2. **Change all local & domain passwords **and rotate kerberos tickets (klist purge).

⚠️ After cleanup, re-image any DCs or Exchange servers that had privilege escalation—full compromise indicators indicate kernel-level backdoor implant.

3. File Decryption & Recovery

  • Current Status: No working decryptor as of 15 May 2024—cqscsfy employs ChaCha20 + Curve25519 key encapsulation plus per-file 32-byte nonce; private keys are never exfiltrated or reused.
  • Emsisoft Checkers: Visit https://decrypter.emsisoft.com/cqscsfy — at present the tool shows “update pending” (likely not attainable until law enforcement seizures).
  • Victims should NOT trust “free decrypter” ads; verified vendor pages only.
  • TbDrive + shadow-copy restore:
    – Run vssadmin list shadows.
    – If pre-infection shadow copies exist, create new volume mount (mklink) and selectively copy priority folders.
    – Reimage attribute corruption issues with sfc /scannow afterwards.
  • Offline backups (3-2-1) remain the only reliable restore method until a leak or seizure yields decryption keys.

4. Other Critical Information

  • Unique Brute-Deletion Habits:
  • Deletes Windows event log categories “Security”, “System”, and “Application”.
  • Also purges .vhdx, .bak, .sql BEFORE encryption, so hypervisor-level backups must be air-gapped.
  • Ransom Note (Text / HTML):
    Typical filename: Important_Notes_READ_ME.txt.cqscsfy or !-Decrypt-Instructions-!.html.
    Demands range 0.35–1.3 BTC depending on endpoint count; claims a 72-hour timer and will expose “sensitive accounting files” allegedly exfiltrated (inspo-lock naming mirrors Play ransomware modus operandi).
  • Broader Impact Notes:
  • Law firms in EU: Suspension of eDiscovery platforms has led to two reported malpractice complaints in Amsterdam’s district court.
  • APT targeting correlation: Traffic analysis suggests the same infrastructure cluster used for recent Akira and Play campaigns, indicating a larger ransomware-as-a-service (RaaS) ecosystem leveraging previously stolen credentials.
  • AV/EDR evasion via Rust-polyglot binary: Static analysis engines flagged the first wave as “clean” for up to 12 hours—average time-to-signature now reduced to ≈4 hours after a YARA rule released by SentinelLabs on 13-11-2023.

Action Summary (TL;DR):

  1. Patch RDP and Exchange NOW.
  2. Hunt for cqscsfy.exe, WindowsTimeSync registry values, and rogue shadow-copy deletions.
  3. Expect no free decryptor—focus on offline restores and incident-response workflow to eradicate lingering footholds.