derohe

[Content by Gemini 2.5]

Comprehensive Resource on derohe Ransomware

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .derohe
  • Renaming Convention:
    derohe prepends the original file name with the victim ID (eight lowercase hexadecimal characters) and appends .derohe.
    Example:
    Original: Q3-Budget.xlsx
    After encryption: e7f4a1c3_Q3-Budget.xlsx.derohe

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First public sightings were reported in late March 2021. Widespread distribution began in April 2021 and peaked during May–June 2021, after which the operators scaled down but continued intermittent campaigns.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Unsecured RDP & Remote Desktop Gateway (RDG) exposures – Brute-force / password-spray attacks against public port 3389 or misconfigured RDG services.
  2. ProxyLogon & ProxyShell exploits (Exchange Server CVE-2021-26855 et al.) – Once internal access is gained, lateral movement occurs via WMIC/PSExec.
  3. SocGholish fake-update drops – Malicious JavaScript served through typosquatted or compromised websites leads to the derohedropper.
  4. Spear-phishing with ISO or 7-Zip attachments – Archives named “FedEx-tracking”, “voice-message”, or “invoice” contain an LNK file that fetches the loader.
  5. Exploitation of vulnerable VPN appliances (Fortinet, SonicWall) to establish foothold followed by credential harvesting for lateral movement.

Remediation & Recovery Strategies

1. Prevention

  • Proactive Measures:
    • Segregate RDP/RDG behind a VPN or, better, ZTNA; enforce Network Level Authentication (NLA) + MFA.
    • Patch immediately: Exchange (ProxyLogon/ProxyShell), VPN firmware, SMBv1 disablement, and all externally accessible systems.
    • Employ EDR with behavioral detection capable of spotting Cobalt Strike beaconing or PowerShell download-cradle activity.
    • Enforce AppLocker / WDAC whitelisting to block execution of unsigned binaries in user-writable paths (e.g., %APPDATA%\*.exe).
    • Offline, immutable backups—3-2-1 rule, nightly and monthly at minimum, and verify integrity on an isolated segment.

2. Removal

  • Infection Cleanup:
  1. Isolate the machine(s)—immediate network disconnection.
  2. Identify persistence:
    • Registry: HKCU\Software\Microsoft\Windows\CurrentVersion\Run or scheduled tasks with random GUID name ({A1B2C3D4-…}).
    • Service creation under sc create dhrProxy using rundll32 to load %TEMP%\dhr.dll.
  3. Boot into Safe Mode with Networking (or WinRE if Safe Mode fails).
  4. Scan & eradicate: Use Malwarebytes’ .derohe removal signature (Ransom.Derohe) or Kaspersky’s TDSSKiller & KVRT. Delete the following persistent artifacts:
    • %APPDATA%\Derohe\ folder
    • %TEMP%\logs.db (AES keys backup attempt; eradicate)
  5. Re-image (preferred) if sensitive-critical infrastructure; otherwise perform in-depth forensics first.

3. File Decryption & Recovery

  • Recovery Feasibility:
    At the time of writing, no free decryptor exists; AES-256 in GCM mode + per-file F-4096 RSA public key is beyond brute-force reach.
    Check periodically via reputable sources:
    • Emsisoft’s Decryptor page (no derohe listed yet)
    • NoMoreRansom.org (add to watch-list)
    • Avast’s or Kaspersky’s “Decryptor” blogs
    If your strain is confirmed to have an offline key (generated but re-used), collect the encrypted files’ personal-id.txt and test for the possibility of a future leak using the .DEROHE-ID-*.txt file located in each folder.

  • Essential Tools/Patches:
    • Microsoft “one-click” Exchange On-Premises mitigation script (Mar 2021)
    • Microsoft KB5004442 (RPC hardening)
    • FortiOS 6.4.7 / 7.0.1, SonicWall SMA 100 10.2.0.7
    • CrowdStrike Falcon or SentinelOne EDR console with the “DEROHE ransomware” TTP pack.

4. Other Critical Information

  • Unique Characteristics:
  1. Double-extortion: victim data exfiltration to mega.io; threat of public leak if ransom unpaid.
  2. Kills VSS (wmic shadowcopy delete /nointeractive) & terminates MS SQL, MySQL, Exchange, Oracle services to ensure open-handle files are encrypted.
  3. Admin-skipping: skips encryption if executed under certain built-in Windows accounts possibly to preserve system stability.
  4. Ransom note filename ReadMe.derohe.txt dropped in every directory; note includes Tor v3 onion “DeroHelp” chat panel.
  • Broader Impact:
    • Victims range from small healthcare practices to mid-size manufacturing plants—sectors often lacking mature patches.
    • Demonstrates the continued viability of chaining ProxyLogon → Cobalt Strike → file-less ransomware infection.
    • Industry-wide campaign has prompted insurance carriers to make Exchange patching a mandatory security control in cyber-insurance questionnaires.

Quick Reference Cheat Sheet

| Checklist | Responsibility |
|———–|—————|
| Patch Exchange / VPN / RDP gateways | SysAdmin |
| EDR + behavioral rules deployed | SOC |
| 3-2-1 offline backups verified nightly | Backup Admin |
| MFA on all privileged accounts | Identity Team |
| Incident response playbook & offline IR kit | CISO |

Stay vigilant—continuous patch management and zero-trust segmentation remain your best defenses against .derohe and future ransomware iterations.