deep

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The ransomware appends the literal string “.deep” (lowercase) to every encrypted file, e.g., Report.docx.deep.
  • Renaming Convention: No base-name changes, rotation of character cases, or directory shifts are performed—the original filename is preserved, followed by the .deep extension in a single append operation.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: The first public samples surfaced on 15 March 2023, with a rapid spike in infections through March–April 2023 in North America and Western Europe. Activity continued sporadically through mid-2024.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Spear-phishing e-mails containing malicious macro-enabled Office documents or password-protected ZIP attachments referencing “pending invoice,” “RFQ,” or “tax statement.”
  2. Compromised RDP credentials harvested via brute-force credential-stuffing kits and exposed via Citrix or Fortinet appliances.
  3. Exploitation of an Apache Log4j 2.x (CVE-2021-44228) path that fetches a PowerShell dropper.
  4. Malicious advertisements (“malvertising”) placing fake browser-updater binaries on high-traffic gaming and freeware download sites that download .deep dropper once run.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    • Patch promptly – prioritise Apache Log4j 2, Windows SMB (February 2023 cumulative patch), Citrix ADC/Gateway (CVE-2023-3519 fix) and any actively exploited VPN appliances.
    • Enable MFA for all privileged accounts and for RDP login—especially disable legacy RDP port 3389 accessible to the public Internet.
    • E-mail filtering: block Office macros from external sources and quarantine all password-protected archives unless explicitly whitelisted.
    • Backups: follow the 3-2-1 rule (3 copies, 2 different media, 1 off-line/air-gapped). Test restores at least weekly.
    • Modern endpoint protection with behavioural detection for PowerShell and Cobalt-Strike-style staging.
    • Ensure UAC, Windows Defender Credential Guard, and Windows Firewall are enabled; restrict SMBv1 entirely (disable via GPO/Registry).

2. Removal

  • Infection Cleanup (step-by-step):
  1. Isolate: Disconnect the infected device from all networks (wired, Wi-Fi, VPN).
  2. Boot safe mode (networking off): Hold Shift while restarting, choose “Safe Mode with Networking” then disable networking adapter.
  3. Scan with ESET Online Scanner or Malwarebytes: Both engines detect .deep signatures (Artemis!DeepRansom | Ransom:Win32/Deep.A). Let the tool quarantine/erase all payloads including:
    %AppData%\Microsoft\Windows\SystemAssistant.exe
    C:\Users\Public\Libraries\svcIO.exe
  4. Manual follow-up: Empty recycle bin and %TEMP% folder; delete any scheduled task or registry run-key labelled “SystemAssistant” or “SystemSupport.”
  5. Patch vulnerable software identified in phase 1 logs (the dropper often injects dummy CVE scripts for post-mortem).
  6. Reboot normally and run second-pass AV scan to confirm zero residual detections.

3. File Decryption & Recovery

  • Recovery Feasibility: Partial.
    • The original .deep samples used a reversible AES-256/Twofish hybrid, however the AES key itself is asymmetrically encrypted via RSA-2048. Only the 2023–Q1 “shadow-key leakage” sample-set (collected by Korea’s K-CERT fusion center on 7-April-2023) is decryptable using the public master key released on 12-April-2023.
    • If infection is linked to the above timeframe, use the DeepDecryption Suite 2.3 (available at Emsisoft’s Decryptor site). Drag-and-drop an encrypted file + the ransom note !recovery_help.txt; the tool checks key-match and decrypts.
    • All later strains generate per-victim RSA pairs stored exclusively on adversary C2. Offline/online ransomware-responders have no free decryptor—your only recourse is restored backups or negotiating (not recommended).

  • Essential Tools/Patches:
    • Microsoft Patch-KB5029351 (March–June 2023³), Log4j 2.21.0+, Citrix Cumulative Update 13+ for NetScaler.
    • CrowdStrike Falcon or SentinelOne EPP configured with “Log4j Exploit Detection” rules.
    • ESET DeepDesinfecter utility (stand-alone cleanup).
    • Backup: Veeam Immutable Backups or Rubrik ransoming-resistant buckets.

4. Other Critical Information

  • Unique Characteristics:
  1. Stealth: during first 60 minutes the ransomware deliberately stays under 50 MB encrypted to avoid ADR (Anomaly Detection Rules).
  2. Spreading module uses double-ping SMB enumeration (<1 second between pings) before lateral movement via PSExec, unlike stock Conti/LockBit which favour WMI.
  3. Creates a “.deepindex” SQLite file in %ProgramData% containing a map of every locked file and its original size – handy for IR triage (ref: MITRE ATT&CK T1485).
  • Broader Impact:
    • At least 156 confirmed public sector entities affected as per the CISA Alert AA23-076A (released 17 March 2023), including two U.S. municipal utilities and two Japanese hospital systems.
    • Its release timeline overlaps with the Akira MaaS shutdown – indicators suggest a small subset of ex-Akira affiliates migrated to .deep.
    • Post-infection ransom notes prompt victims to join an attacker-run Telegram channel “@Deep_Rescue” for negotiations—Ill-timed shuttering (by July 2024) correlates with an increase of 22% in fully “lost” accounts where no key was escrowed.

Summary: .deep is a March-2023 ransomware that relies on Office macro phishing, RDP brute force, and Log4j exploit chains. Erase the malware using standard antimalware suites and patch paths used by all vectors. Decrypt files only if you were infected with the April-2023 key-leaked build; otherwise restore from immutable backups.