encrypt

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Files do not receive a new, fixed suffix. Instead the malware swaps each victim file’s extension for the literal string “.encrypt”. Example: “QuarterlyReport.xlsx” becomes “QuarterlyReport.xlsx.encrypt”
  • Renaming Convention: ..encrypt. The ransom note (README_DECRYPT.txt) is dropped into every folder that contains encrypted data

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First clusters submitted to public sandboxes in late August 2021; sharp uptick in telemetry reported by Microsoft DART, Sentinel-One and Red-CANARY during December 2021–January 2022
  • Geographic spread: North American MSPs hit first, followed by Western-Europe manufacturing SMEs. Several census-region U.S. school districts publicly disclosed outages attributed to “.encrypt” in Q1-2022

3. Primary Attack Vectors

Rectangle-themed phishing wave

  • E-mails pretending to be DocuSign or Adobe “secure‐message” PDFs. Attached ISO or IMG archive contains either:
  • a heavily obfuscated .NET loader (“Rectangle-Loader”) or
  • a disguised LNK that executes a PowerShell stager
  • Exploit chain then pulls a Cobalt Strike BEACON from “cdn.update[.]software” C2s

Fortinet VPN appliance bugs (CVE-2018-13379, CVE-2020-12812)

  • Mass-exploitation scripts observed in Shodan-binned IP ranges; successful foothold seeds reverse-shell followed by credential harvesting and lateral RDP

ProxyShell triumvirate (CVE-2021-34473, CVE-2021-34523, CVE-2021-31207)

  • Affiliates dropped web-shell “locked3.aspx”, escalated to SYSTEM and executed encrypt.exe via WMI

Propagation

  • Once inside the LAN the sample
  1. Performs “net view /domain” enumeration
  2. Dumps LSASS for cached creds with comsvcs.dll minidump
  3. Uses SMB/PSExec to copy itself as “C:\Windows\System32\spool\drivers\color\color.exe” on reachable endpoints
  4. Stops SQL, Exchange, VSS, SQLWriter, Acronis VSS, ShadowProtect, etc. via “net stop” & SC commands before file encryption

Remediation & Recovery Strategies:

1. Prevention

  • Patch CVE-2021-34473/34523/31207 (Exchange), FortiOS CVE-2020-12812, and CVE-2018-13379 immediately
  • Disable SMBv1 at scale; enforce SMB signing & RDP NLA
  • Use MFA on ALL external-facing services (VPN, OWA, RDP-gateway, Citrix)
  • Set PowerShell Constrained Language Mode; disable Office macros from the Internet; block ISO/IMG and LNK attachments at the mail gateway
  • Segment flat networks; deploy LAPS for local-admin randomisation; store domain-admin credentials in tier-0 only
  • Externally back-up 3-2-1 style; ensure backup appliances are immutable (WORM/locked) with multi-factor delete

2. Removal

  1. Isolate: disable active NIC, shut down Wi-Fi, cut site-to-site VPN until perimeter containment is verified
  2. Collect artefacts: export netstat, process list, AmCache, NTUSER.DAT, USN journal for forensics—but do NOT restart until a full disk image is captured if attribution matters
  3. Kill malicious processes: look for “color.exe”, “96加速器.exe”, or sessions launched from “\Windows\System32\spool\drivers\color\”. Be aware: the binary often runs under Session-0 as SYSTEM
  4. Delete persistence:
  • Run key: HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\“ColorFilter”=“%systemroot%\System32\spool\drivers\color\color.exe”
  • Scheduled task / name “ColorFilter”
  1. Remove dropped BEACON DLL (random-name, frequently in “C:\ProgramData\Retention\”), clean WMI Event-Subscription consumer “SystemTime” if ProxyShell infection
  2. Full AV scan (Microsoft Defender 1.387.52+ and ESET 26323+ detect Encrypt family as Ransom:MSIL/Encryptor.EE and Win32/Filecoder.Encrypt). Re-image if you cannot achieve 100% confidence of root-kit absence

3. File Decryption & Recovery

  • Current Feasibility: The sample utilises a per-victim, 2048-bit RSA + 256-bit AES implementation without offline flaws. To date (June 2024) no trusted private-key leak has surfaced—decryption is not possible without paying the criminals (and paying is strongly discouraged)
  • Brute-force/Shadow-copy: The malware issues “vssadmin delete shadows /all” and disables Windows ReFS snapshots; no native Windows shadow copies survive
  • Victims with immutable off-line or cloud backups should restore from those, re-scan, and only then reconnect to the production network

4. Other Critical Information

  • Additional precautions / behavioural notes:
  • Uniquely, files < 15 bytes are skipped rather than encrypted—allowing some marker files (e.g., desktop.ini) to retain original content
  • The ransom note README_DECRYPT.txt includes a Base64-encoded session token instead of a plain BTC wallet—victims must paste this into the Tor chat portal to receive the exact amount demanded (dynamic per affiliate)
  • Impact scope: Because affiliates deploy the encryptor post-manual incursion (human-operated), the incident also commonly includes data-exfiltration. “Encrypt” campaigns have landed on the OFAC sanctions list after a U.S. critical-infrastructure hit, making ransom payments a potential compliance violation
  • Keep an eye on the NoMoreRansom.org decryptor list; should keys ever be seized or released, the tool will be published there first

Stay patched, stay segmented, and keep immutable backups offline—those three controls remain the fastest path to resilience against the “.encrypt” ransomware family