encrypted_.enc_robbinhood

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RobbinHood Ransomware (.enc_robbinhood) – Community Response Guide

(last updated: 27 June 2025)

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmed extension: .enc_robbinhood (sometimes appears as encrypted_.enc_robbinhood)
  • Renaming convention:
  • Original file Quarterly.xls → Quarterly.xls.enc_robbinhood
  • Folder-wide rename is atomic – no second extension is added, so backups with “.bak” or “._temp” are also overwritten in-place.
  • No email/ID string is injected into the filename (unlike Dharma), making quick visual triage harder.

2. Detection & Outbreak Timeline

  • First public sightings: 23 Apr 2019 (Baltimore City government network)
  • Major waves:
  • Dec 2019 – green-energy firms in Spain & Portugal
  • Apr 2020 – healthcare clusters in U.S. Midwest (COVID-19分心)
  • Oct 2022 – MSSP supply-chain incident (RMM tool compromise)
  • Mar–Apr 2025 – re-emergence with signed kernel driver (see 4. Other)
  • Peak activity months: April & October of each calendar year (tax & budget cycles).

3. Primary Attack Vectors

  1. Bring-Your-Own-Vulnerable-Driver (BYOVD)
  • Drops legit but expired Gigabyte gdrv.sys (CVE-2018-19320) or ASUS ATSZIO.sys (CVE-2021-26639) to kill AV/EDR.
  1. Exploitation of unpatched Windows SMB (not EternalBlue)
  • Uses stolen domain credentials + PsExec to push payload to every reachable ADMIN$ share.
  1. RDP / Terminal-services brute-force followed by manual “hands-on-keyboard” activity
  • Average dwell time: 4–7 days; adversary manually disables Windows Defender via Group Policy.
  1. Software supply-chain
  • 2025 variant pushed via trojanised update of a remote-management agent; installer was signed with revoked but still-trusted code-sign cert.
  1. Phishing is rare – RobbinHood is almost entirely “human-operated” after external perimeter breach.

Remediation & Recovery Strategies

1. Prevention

  • Patch & harden:
  • Remove or update the following drivers if unused: gdrv.sys, AsUpIO.sys, AsIO.sys, ATSZIO.sys, RTCore64.sys.
  • KB4499154 (Servicing-stack) and current cumulative updates block the 2025 signed-driver variant.
  • Credential hygiene:
  • Disable LANMAN, restrict RDP to whitelisted jump hosts, enforce 14+ char service-account passwords, use LAPS.
  • Network segmentation:
  • Separate VLAN for workstations, servers, DCs; DENY ALL SMB/445 between user VLANs.
  • Application control / Driver blocklist:
  • Deploy Microsoft WDAC or HVCI with Microsoft’s “Vulnerable Driver Blocklist” (2025-05 refresh).
  • Controlled folder access (Windows 10/11) – add cover for C:\Users, SMB shares, and Veeam/BackupExec repos.

2. Removal / Incident-Cleanup Workflow

  1. Contain:
  • Isolate DCs last – but power-off infected member servers immediately to stop encryption thread.
  1. Collect artefacts:
  • C:\Windows\Temp\*_robbinhood.exe, C:\Windows\Temp\robbinhood_*.*, C:\Windows\System32\drivers\{gdrv,ATSZIO,RTCore64}.sys
  • readme_RestoreFiles.txt, _Decryption_ReadMe.html, RSA_Pub.key
  1. Delete persistence:
  • Delete service “RobbinHood” (display-name: “InOrg Tracker”).
  • Inspect WMI EventFilter BhaFilter.
  • Remove Run key HKLM\Software\Microsoft\Windows\CurrentVersion\Run\SvcInOrg.
  1. Driver clean-up:
  • Boot into Safe-Mode with Networking → sc query gdrv → sc stop gdrv → sc delete gdrv → delete the .sys file.
  1. AV/EDR resuscitation:
  • After vulnerable driver is gone, reinstall or start Windows Defender/SEP/Sentinel and run full scan.
  1. Patch & reboot.
  2. Reset all domain passwords (Krbtgt twice) and force log-off.

3. File Decryption & Recovery

  • Free decryptor? NO. Files are encrypted with RSA-4096 (public key embedded) + AES-256-CTR per file; private key never leaves attacker C2.
  • Brute-forcing is computationally infeasible.
  • Recovery paths:
  1. Offline backups that are NOT addressable via SMB/iSCSI. RobbinHood explicitly enumerates and deletes VSS, WBADMIN, SQL dumps, and common backup file extensions (.vbk, .bk2, .bkf).
  2. Volume-shadow “ghosts”: On Server 2019+ with ReFS + Block-Cloning backups, use Microsoft’s refsutil salvage – occasional success when shadows were stored on separate ReFS volume.
  3. File-carving / optical media: If data was archived to ISO/IMG outside the mounted file-system, carve with PhotoRec.
  4. Paying the ransom: Historically attackers do supply a working decryptor, but payment supports criminal activity and is legally prohibited in certain jurisdictions. Get legal advice and log OFAC screening before even considering.

4. Other Critical Information

  • Unique behaviour:
  • Drops two ransom notes (TXT & HTML) but also donates $10 000 (in 2019) to two mega-charity wallets – PR stunt to portray attackers as “Robbin Hood”.
  • Driver-based kill-chain allows it to work fully offline once delivered – no embedded C2 address in the encryptor binary (thwarts sandbox detonation).
  • Broader impact:
  • City of Baltimore spent ~$18 million in recovery (2019).
  • 2025 variant signed with stolen EV cert bypasses SmartScreen and driver-signature policies on fully-patched Windows 11 23H2.
  • Regulatory / legal:
  • Some insurance carriers now list RobbinHood as “nation-state like” because of its cost profile; review policy exclusions.
  • U.S. Treasury OFAC advisory 2021-09-21 still applies – any payment to associated BTC addresses (see IOCs) risks civil penalty.

IOC Quick-Reference (non-exhaustive)

File hashes (2025 wave)
0fa83…c1bc (dropper)
4be2a…90af (RTCore64.sys)
f47bc…11c3 (main encryptor, .NET 6)

BTC wallets (do NOT pay – sanctioned)
1LKW…9cG
3JvT…Xeo

Registry keys
HKLM\SYSTEM\CurrentControlSet\Services\RobbinHood
HKLM\SOFTWARE\InOrg

C2 used during staging (usually offline during detonation)
updates-status[.]biz, ssl-galvanize[.]com

TL;DR for System-Administrators

RobbinHood is offline ransomware that weaponises legitimate, vulnerable kernel drivers to blind security tools. There is no free decryptor; secure backups disconnected from AD/SMB are the only reliable recovery path. Patch or remove the listed drivers NOW, tier your admin credentials, and segment your network before the next April wave hits.