dcrtr

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: Files encrypted by Dcrtr are renamed with the suffix .dcrtr.
  • Renaming Convention: [original_name].[original_ext].id-[8-hex-chars].dcrtr, e.g.,
    Budget_2024.xlsx.id-3AFB12AC.dcrtr.
    Some campaigns embed the campaign ID or the operator’s “client name” between the victim-ID and the final extension:
    .id-F28D1FB0.[alien].dcrtr

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First public sightings early February 2018. A massive re-branding wave occurred June 2019 after added .dcrtr variants (wallet sub-families). Siginificant resurgence in Q4-2020 through Ilance loader network and breached RDP sessions.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  • RDP bruteforce & credential stuffing – most dominant: thousands of weak RDP endpoints exposed to the Internet become drop zones.
  • Spam / malspam – Office documents embedding malicious VBA droppers or JavaScript downloaders (Nemucod, Houdini).
  • Software-exploit combos – bundled with RIG, GrandSoft, and Fallout exploit kits; in 2020 it abused CVE-2019-2725 (WebLogic) to gain foothold.
  • Compromised upload portals & SMB shares – attackers move laterally via SMBv1 or harvest saved passwords to pivot.

Remediation & Recovery Strategies:

1. Prevention

Immediate, high-impact actions:

  1. Close port 3389 (RDP) to the open Internet; require VPN + MFA for remote access.
  2. Enable Network Level Authentication (NLA) and enforce complex, globally-unique passwords (≥15 chars).
  3. Patch external-facing servers – especially Windows SMBv1 (MS17-010), Remote Desktop Services (BlueKeep CVE-2019-0708), Oracle WebLogic CVE-2019-2725.
  4. Restrict Office macros via Group Policy; only allow signed macros from trusted publishers.
  5. Maintain offline + off-site backups (3-2-1 rule) with write-protection/low-privilege service accounts for staging share.
  6. Segment networks: separate backup VLAN, lateral-traffic firewalling between internal subnets.

2. Removal

  1. Isolate – disconnect affected host from LAN/WAN; disable any active iSCSI connections to block encryption across mapped drives.
  2. Identify & kill – look for the randomly-named EXE (avg 1–6 MB) in %TEMP%, %APPDATA%\Roaming, or C:\ProgramData\Microsoft. The ransom note is named HOW TO DECRYPT FILES.txt or Decryptor.hta; these drop in every folder.
  3. Boot to Safe Mode with Networking and run a current offline AV engine (ESET, Kaspersky RescueDisk, Microsoft Defender Offline). Add scheduled task deletions under:
    HKCU\Software\Microsoft\Windows\CurrentVersion\Run, Task Scheduler\Library (look for suspicious crypto-named tasks).
  4. Scan credentials file stores (mimikatz output, browser vaults) and rotate all privileged passwords.

3. File Decryption & Recovery

  • Recovery Feasibility: At the time of drafting (2024-06) NO reliable decryptor exists. Dcrtr utilizes secure AES-256 key encapsulation via Curve25519 (CryptGenRandom), then pushes the private key to the threat actor’s server.
  • STOP/Djvu decryptor by Emsisoft (Oct 2021 variant) does not work on recent .dcrtr strains.
  • Boot-level journaling (VSS / shadow copes) is usually wiped via vssadmin delete shadows /all.
  • Essential Tools/Patches:
  • Microsoft MS17-010 security update.
  • Cisco Talos NMap NSE script rdp-brute.nse for post-incident audit.
  • Duplicati 2 or Veeam Community Edition for nightly immutable backups.

4. Other Critical Information

  • Unique Characteristics:
  • A “CPU count to sleep” anti-VM technique: delays processing if ≤2 cores found—common in old Windows 7 lab environments.
  • Uses MAPI to harvest addresses from Outlook and feeds back into spam campaigns—self-spreading via infected mailboxes.
  • Specifically targets accounting software (Sage 50, QuickBooks .qbw) to maximize ransom willingness.
  • Broader Impact:
  • 2020 wave (dcrtr-paradise fork) encrypted 35 hospitals in Europe, leading to patient diversion and supply-chain downtime.
  • Payment demand escalated from 0.3 BTC (2018) to 1.2–2.5 BTC in 2023 (~US $30-60 k) with a 72 h countdown; non-payers often see operator auctioning the leaked folders on HelenDark forum.

Action-oriented takeaway: Assume decryption is impossible for .dcrtr and invest fully in resilient, air-gapped or immutable backups. Every additional hour spent on prevention and restoration planning directly reduces the risk—and cost—of this ransomware family.