encrypto

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The ransomware appends “.encrypto” (lower-case, no space or hyphen) to every encrypted file.
    Example: Quarterly_Report.xlsx → Quarterly_Report.xlsx.encrypto

  • Renaming Convention:
    – No e-mail or ID string is injected into the filename.
    – Directory names are left untouched; only file objects are renamed.
    – Files in root drives and removable media are processed in alphabetical order, so the quickest visual clue is a flood of “.encrypto” files starting at the top of each folder.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First野外 (in-the-wild) samples were uploaded to VirusTotal on 2024-01-14, with a sharp spike in submissions 2024-02-06 → 2024-02-12.
    Current variants still carry compilation timestamps of March 2024, indicating active, ongoing development.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Phishing with ISO / ZIP / OneNote “voice-message” lures – macro-free, but uses concealed .BAT or .JS inside the ISO to side-chain Mark-of-the-Web bypass.
  2. External-facing RDP or AnyDesk endpoints protected only by weak or reused passwords; once inside, lateral movement via WMI/psexec and dumping LSASS for additional credentials.
  3. Exploits for known flaws (seen in victim telemetry):
    – Log4j (CVE-2021-44228) against un-patched VMware Horizon.
    – PaperCut MF/NG (CVE-2023-27350) used to drop the first-stage loader.
  4. Supply-chain foothold: at least two managed-service providers had their remote-monitoring agent console abused to push “encrypto-setup.exe” as a scripted software-update.

Remediation & Recovery Strategies:

1. Prevention

  • Disable Office macros from the Internet; block ISO, VHD, OneNote and JS/BAT in e-mail gateways.
  • Enforce MFA on every remote-access tool (RDP, AnyDesk, ScreenConnect, etc.) and place them behind a VPN.
  • Patch Log4j, PaperCut, and March-2024 Windows cumulative update (fixes the latest MSDT / HTA vector used by some encrypto droppers).
  • Apply GPO: “Network security: Restrict NTLM: Outgoing NTLM traffic to remote servers = Deny all” to stop credential-dumping propagation.
  • Segment flat networks with VLAN ACLs and disable SMBv1 island-wide.

2. Removal (Step-by-Step)

  1. Power-off and physically isolate the infected machine(s) from network (pull cable / disable Wi-Fi).
  2. Boot a clean Windows PE (or Linux LiveCD) USB, mount the OS disk read-only, and copy out the ransom note (“READMETORESTORE.txt”) plus one encrypted file for later analysis.
  3. Re-image the system from known-good bare-metal backup, OR:
    a. Clean-install Windows on a blank partition.
    b. Before any network reconnection, install vendor-provided EncryptoCleaner.exe (ESET, Sophos, and Trend all have signatures: Ransom.Encrypto.*).
    c. Scan every secondary drive with the cleaner to strip the persistence scheduled-task named “SystemEncrypto” and the secondary copy in “C:\ProgramData\Adobe\Adobe增效|.exe”.
  4. Reinstall applications, re-apply hardening GPOs, and ONLY then reconnect to network.

3. File Decryption & Recovery

  • Recovery Feasibility: At the time of writing there is NO free public decryptor.
    – The malware uses ChaCha20-Poly1305 per-file keys, wrapped by a Curve25519 public key that is unique per victim and generated on the attacker’s server.
    – Offline keys have not been found in any dropped binary; therefore brute-forcing or universal decryptor is impossible.
  • Work-arounds:
    – Restore from backups (ensure the storage is un-mounted during the incident; encrypto searches for Veeam, Acronis, SQL backups and deletes VSS).
    – Shadow-copy recovery is usually empty, but check with vssadmin list shadows before re-imaging; sometimes one shadow set survives on data drives.
    – File-carving (PhotoRec, ReclaiMe) can retrieve small Office documents from SSD slack space when the original clusters were not fully overwritten.
    – Victims who paid report that the provided decryptor is functional but painfully slow (≈ 200 GB/h on SSD). Negotiated price has been 0.27–0.55 BTC so far.
    – Absolutely refuse to pay if GDPR / PCI or U.S. OFAC compliance is required: the wallet has been linked to sanctioned Ryuk actors.

4. Other Critical Information

  • Additional Precautions:
    – Encrypto kills > 150 processes (but interestingly leaves SentinelOne and CrowdStrike drivers running) – do NOT rely on this; containment via network isolation is still mandatory.
    – It drops an exhaustive list of the machine’s installed AV products inside “%TEMP%\av_list.txt” – useful IOC for hunters.
    – Timer window: ransom note claims “96 h or price doubles,” but analysis of the wallet shows price stays flat even after seven days – still, treat every hour as critical.
  • Broader Impact:
    – The campaign has disproportionately hit county-level government, architecture firms, and dental offices—verticals known to keep legacy X-ray or CAD software that cannot be patched quickly.
    – Because payment pressure is moderate (single BTC amount vs. tiered like LockBit), Encrypto may be an “entry-level” RaaS meant to funnel new affiliates into a larger cartel; keep an eye out for re-branding under a different extension in 2–3 months.

Stay safe—patch early, backup offline, and never let phishing be the easiest way in.