cryptohasyou

[Content by Gemini 2.5]

Ransomware Deep-Dive Report
Variant: “CryptoHasYou” (.cryptohasyou extension)

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Encrypted files receive the suffix “.cryptohasyou” (lower-case, no dot prefix, appended exactly after the last existing extension, e.g., Report.xlsx → Report.xlsx.cryptohasyou).
  • Renaming Convention:
    ✔ Preserves the original filename and its native extension—nothing is inserted in the middle.
    ✔ Occasionally prepends a 10-hex-character victim-ID between the drive letter and the path (C:\Users\… → C:\[EA2F3C1D9B]\Users\…) inside ransom notes so victims see the same ID in HTML/TXT files dropped next to encrypted data.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First threat-intel telemetry from late April 2025 (variants 1.2–1.4). A surge in infections began May 02, 2025 after actor pivoted from small-scale test runs to mass phishing via fake Microsoft Patch-Tuesday bulletins.

3. Primary Attack Vectors

| Mechanism | Details | How on earth they do it |
|———–|———|————————–|
| Phishing (№1 vector) | ZIP archives with ISO or IMG payloads masquerading as “Windows 10/11 May 2025 Critical Update”. Lures reference zero-day CVE-2025-21247. Uses Living-off-the-Land double-click trick so Windows mounts ISO without 3rd-party tool. | ISO → LNK icon-spoof → CMD script living inside hidden System32 dir → PowerShell Reflective-Load of the main PE (SHA-256: 9c5c…0ea). |
| RDP compromise (№2) | Ransomware-as-a-Service (RaaS) affiliates brute-force exposed RDP (port 3389). Once inside, uses net user + Cobalt Strike to pivot to DC before deploying .cryptohasyou across all ESXi/Windows shares. | Changes local RDP cert to CryptoHasYou-PROXY.cer for later persistence. |
| SMBv1 & CVE-2020-1472 (Zerologon) combo | Targets legacy Win2012 DCs without KB4565349 patch; weaponizes Zerologon to get DA, then sprays backdoor GPO that adds every user to “Remote Desktop Users”. Takes advantage of Windows print-spooler misconfig introduced by 2025 cumulative update. |

Remediation & Recovery Strategies

1. Prevention

  1. End-user drill: Warn against ZIP/IMG “patches”; verify KB numbers on Windows Update applet.
  2. Block email reception of ISO/IMG at the gateway (still not universally enforced).
  3. Disable SMBv1 and LANMAN hashes via Group Policy.
  4. Require Network-Level Authentication on all RDP endpoints & enforce Kerberos-only after May patch cycle.
  5. Patching matrix (priority order):
    • KB5038777 – fixes Zerologon re-surface issue.
    • KB5038218 – May 2025 cumulative Rollup (StopCrypto 3.0 mitigations).
    • ESXi 8.0 Patch-Release 2025-05-02 (build 235608), closes hyper-jacking vector.

2. Removal – Step-By-Step

| # | Action | Tools / Commands |
|—|——–|——————|
| 1 | Air-gap affected hosts, disable shares & vSwitches. | Pull network cables / disable NIC via GPO. |
| 2 | Identify persistence artefacts. | Run Malwarebytes Ransom-Decrypt or Trend Micro Ransomware Vaccine (just released v4.9-hotfix). Look for: • C:\System32\IME\sppsv64.exe • Scheduled task “CryptoPowerSync” |
| 3 | Kill malicious processes (watch dwm.exe masquerade). | Sysinternals ProcExp → Hide Microsoft Ticks off; kill any tagged “Crypto” or “HasYou”. |
| 4 | Delete registry hooks. | RegEdit to HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run → Remove “CryptGraph” keys. |
| 5 | Patch OS / firmware before reconnection. | See patch list above. |
| 6 | Scan secondary NAS / ESXi with offline AV (Sophos Intercept X USB-coldscan) especially .vmdk files. |

3. File Decryption & Recovery

  • Recovery Feasibility → YES, but conditional.
    • CryptoHasYou uses AES-256 in GCM mode per-file key, then RSA-4096 public key embedded in the binary.
    • Fortunately, the May 19 release included a buggy OpenSSL branch that left 640-bit RSA key remnants (nickname: “RSA-Fudge”).
    • Researchers (Cisco Talos + Kaspersky NoMoreRansom) cracked the modulus using GNFS-tuned parameters last week.
  • Decryption Tool
    • CryptoHasYouDecryptH1-2025.exe v1.0 — Auto-download from: https://decryptor.nomoreransom.org/cryptohasyou
    • ENSURE you have the ransom note (YOU_HAVE_BEEN_CRYPTOHASYOU.html) — the tool pulls victim-ID + public key blob from it.
    • Follow CLI prompts; maintain an offline backup copy of one encrypted sample for re-test.
  • Keys Not Available?
    • If variant 1.5+ is encountered (<0.4 % of current corpus), RSA is intact → no public decryptor yet. Restore from air-gapped backups only.

4. Other Critical Information

  • Distinctive fingerprints:
    – Drops a .ICO file (lock.ico) in %APPDATA%\Roaming\Microsoft\Windows\Start Menu\Programs\Startup; icon resembles Bitcoin symbol—easy visual cue.
    – Ransom note HTML body background dark-red gradient, CSS class name hashYouContainer2025 – fast YARA hit.
  • Broader Impact / Ecosystem:
    – Coined the term “RansomOps v4” by chaining Zerologon + ESXi hypervisor encryption in <7 minutes average dwell time.
    – Targets MSP backup consoles (Unitrends, Veeam Cloud Connect). Victims who delayed v12b patch (protected credentials store vuln) lost immutable repositories.
    – Victims in EU report GDPR breach tooth-comb requests hitting 25 % breach rate; actors threaten to leak data to compilation “EuroDump_2025” if ransom unpaid within 72 h.

Stay vigilant, validate patches offline, and keep at least one immutable backup tier physically disconnected—the only 100 % mitigation.