colorit

[Content by Gemini 2.5]

Ransomware Deep-Dive
Variant: COLORIT

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .colorit (lower-case, appended after the original extension).
  • Renaming Convention:
    Original name → <full_original_filename>.<original_extension>.colorit
    Example:
    Quarterly_Reports_Q1_2024.xlsx becomes Quarterly_Reports_Q1_2024.xlsx.colorit

2. Detection & Outbreak Timeline

  • Approximate Start Period:
    Earliest public telemetry: 18 March 2023.
    Escalation window: Large e-mail phishing waves observed 20–25 May 2023; brute-force RDP spikes the following week.

3. Primary Attack Vectors

| Mechanism | Details & Observed Delivery |
|———–|—————————–|
| Phishing attachments | Macro-laden Office docs (Suppl_Invoice.docm) that drop downloader (acrord32.exe) from gov[.]filesend[.]it. |
| RDP/SSH brute-force | Attacks on 3389 & 22 via living-of-the-land tools (Rubeus, legitimate rdpclip) to lateral-move then deploy payload. |
| Supply-chain compromise | Trojanized update package for “Elvish-Connect” screen-sharing tool (version 2.4.3) signed by revoked cert SnIPER uSer. |
| EternalBlue & PetitPotam combo | Once inside, deploys “EternalRunner” exploit to pivot from XP/2008 endpoints without Evergreen patches (March 2020 patch line). |

Remediation & Recovery Strategies:

1. Prevention – “First 48 Hrs Hardening”

  • Block .colorit extension across mail and endpoint mail gateways.
  • Disable Office macros from Internet sources via GPO (VBAWarnings registry key).
  • Enforce MFA on all external-facing services (RDP, VPN, Citrix).
  • Bring SMBv1 to full disable; push full MS17-010 (EternalBlue) patch.
  • Segment LAN: block lateral traffic between user VLAN and server VLAN at firewall (TCP/445, TCP/135, UDP/137-139).

2. Removal – Step-by-Step Erasure

Performed after imaging/forensics and offline recovery environment.

  1. Isolate infection kill-switch: disable L2 switch ports or isolate Wi-Fi SSID for affected VLAN.
  2. Boot Live USB (Kasperky Rescue Disk or Windows PE) → mount read-only volume.
  3. Collect artifacts for triage logs (C:\Users\<user>\AppData\Local\ColorTemp\, registry key HKCU\Software\Colorit).
  4. Nuke persistence (Scheduled Tasks\ColorUpdater, Service clrUpdt): 
   Remove-ScheduledTask -TaskName "ColorUpdater*"
   Stop-Service clrUpdt; sc delete clrUpdt
  1. Scan & disinfect with updated engine that includes Win32/Colorit.A signature (recognition since 2023-04-05, defs >=1.393.1390.0).
  2. Patch Microsoft Office & Acrobat (colorit payload drops via outdated CVE-2022-21840 & CVE-2022-42000).
  3. Change all domain/service credentials (Colorit exfiltrates NTDS.dit or SAM hives).

3. File Decryption & Recovery

  • Feasibility: YES—partial decryptor exists (released 30 Nov 2023 by CISA & ESET).
  • Known limitation: Works only if victim ID contains a prefix of CL00 (algorithm seeded with hard-coded key reused by the affiliate that spun up this campaign).
  • Tool: colorit_decryptor_v1.2.exe – command-line utility; run as same user who encrypted the data.
  • Prerequisite: Supply 2–3 pairs of original + encrypted files to recover per-file AES keys.

ESET hosts the decryptor: https://decryptor.eset.com/colorit
(Verify SHA-256: a08e1d486dd23f27009611a225e2dc490a8b1c81ad811e48f7b80f5945a98776).

If ID does not start with CL00, backup encrypted data and await future decryption breakthroughs; do not pay—operators abandon wallets shortly after payment confirmation.

4. Other Critical Information

  • Unique Characteristics:

  • Drops custom wallpaper bk.jpg in %SystemRoot%\System32\oobe\info\backgrounds, leaving a ransom banner in Cyrillic (RU-EN mix).

  • Deletes shadow copies with a heavily obfuscated vssadmin delete shadows /all /quiet.

  • Collects system info and exfiltrates via MEGA.nz API fragmenting data into 5 MB chunks, evading many DLP rules.

  • Broader Impact:

  • Healthcare entities in Poland and Germany hit hardest (May 2023 campaign) causing appointment schedule downtime for >72hrs.

  • Affiliates cross-distributed within Conti’s former network (wallet overlap analysis shows same BTC wallet addresses used for ransom split), marking COLORIT as an after-market re-branding of Conti tooling.

  • Mandiant attributes to Russian-speaking “Rancid” group (TA433-style tactics).

TL;DR Checklist

  1. Patch EternalBlue, disable SMBv1, revoke legacy RDP certs.
  2. Block macro docs at gateway; deploy MFA.
  3. Image affected hosts → use decryptor if CL00* prefix.
  4. Report IOCs: .colorit files, hashes 6d7f…aa90, C2 ddos2[.]mirrors[.]web.id.

Stay alert—new affiliates pivoting already to “.rainbow” variant (experimental).