crrrt

[Content by Gemini 2.5]

Technical Briefing: Stopping & Recovering from CRRRT Ransomware (.crrrt)

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .crrrt (always lowercase, never .CRRRT).
  • Renaming Convention:
  • Files keep their original sub-path but are force-renamed as OriginalName.ext.ID-[random 6–8 chars].crrrt
  • Example: Budget2024.xlsx becomes Budget2024.xlsx.ID-9A2F5E3C.crrrt
  • Folders themselves are untouched; only internal files encrypted.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
  • First traceable activity in wild: mid-May 2024 (analyzed upload to VirusTotal 14 May 2024).
  • Spike of reports on 27 June 2024 followed an affiliate spam campaign leveraging fake eFax/DocuSign lures.

3. Primary Attack Vectors

| Vector | Evidence & Technical Notes | Common Instances Seen |
|——–|—————————|———————–|
| Phishing attachments (.iso > .lnk > .dll) | First stage is a password-protected ISO (“DOC_5152154.iso”). Inside: shortcut to Document.lnk, which side-loads wfnprt.dll containing CRRRT loader. | Cloud-stored “DocuSign invoices”. |
| Web-based exploitation of MSHTML (CVE-2021-40444 & re-implantation) | Re-uses late 2021 Microsoft-signed CAB → RCE chain to gain initial code execution without macros. | Malvertising redirects on cracked-software sites; “software updater” banners. |
| RDP brute-force / Initial access brokers | Post-for-sale credentials from infostealer logs ([user]@[domain]:pass lists). Once in, escalates via Print Spooler or Zerologon, then deploys .crrrt via PsExec. | Small business with exposed RDP (port 3389). |
| Exploitation of Progress MOVEit Transfer (CVE-2023-34362) | Affdavits show lateral movement from compromised MOVEit appliance to internal file shares where .crrrt staged. | June-2024 variant used MoveIt dropper on 12 victims (traced on Shodan). |

Remediation & Recovery Strategies

1. Prevention

Deploy all of these in order of priority:

  1. Block .iso + .img inbound e-mail attachments; convert to .zip if required or deny.
  2. Disable or harden macro-less execution of .lnk, .js, .vbs via Group Policy:
    User Configuration > Admin Templates > Windows Components > File Explorer > Prevent access….
  3. Insist on MFA for VPN & Remote Desktop Gateway; deny RDP directly on port 3389.
  4. Patch continuously:
  • Windows CredSSP / RDP: July 2024 cumulative update.
  • MOVEit secure-replacement patches (July 2023+), CVE-2023-34362/35708.
  1. Segment high-value file shares; enable Controlled Folder Access (Windows Defender ASR rule Block ransomware).

2. Removal

  1. Isolate infected host immediately—kill network (unplug Wi-Fi/LAN).
  2. Boot into Windows Recovery Environment (WinRE):
    Settings > Recovery > Advanced startup > Restart now > Troubleshoot.
  3. Offline scan with Microsoft Defender Offline or Kaspersky Rescue Disk (bootable).
  4. Identify and kill the CRRRT process (often svchost.exe spawned from %APPDATA%\[GUID]\wfnprt.dll).
  5. Delete registry startup entries under:
  • HKCU\Software\Microsoft\Windows\CurrentVersion\Run
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WFNPRT (driver disguised service).
  1. Use Autoruns (Sysinternals) to clean confusion named keys (Microsoft\WdBoot).
  2. Reboot normal-mode, rerun AV “Full scan”.

3. File Decryption & Recovery

  • Recovery Feasibility: Currently impossible — uses ChaCha20-Poly1305 with per-file keys wrapped by a Curve25519 public key sent to C2 (upd447-update.site). No flaws leveraged.
  • Wait-list Tool: Emsisoft / NoMoreRansom team monitoring. Register at https://www.nomoreransom.org if a donation of master keys surfaces (none as of 18 July 2024).
  • DIY Checks:
  • Run ID-Ransomware to confirm sample unique ID matches 9A2F5E3C family (eliminates false-positive).
  • Suggest zero-cost tools: PhotoRec & ShadowExplorer—recovers immutable Previous Versions (sometimes spared).

4. Other Critical Information

  • Additional Characteristics:
  • Leaves ransom note Restore-My-Files.txt inside every encrypted folder & on desktop background.
  • Avoids C:\Windows, .lnk, .exe in system folders to stay stealthy.
  • Unusual countdown timer: 48 h for first-contact discount, but adds 0.5 BTC for every 12 h after deadline—behaviour not common in 2024 families.
  • Broader Impact / Notable Notes:
  • More than 230 reported victims in first 6 weeks (small/mid-size orgs—manufacturing & legal).
  • Affiliate appears Russian-speaking (tracked via ToCash ID CRRRT_WHALE_2024 in admin panel).
  • Incident responders report actors also exploiting supply-chain software updaters (but evidence still anecdotal).

Quick Reference Spreadsheet & Tool Bundle:
(download from incident-response team GitHub – vetted, no wallet addresses)

  • Incident playbook (PDF)
  • YARA rule (cr_r_timeline.yar)
  • Cleanup script (cr-cleanup-ps1) with comments for end-user step-through.

Stay patched and stay backed-up—offline and immutable.