bkp

[Content by Gemini 2.5]

Technical Breakdown – “.bkp” Ransomware (T-REX / CryT0x variant)

1. File Extension & Renaming Patterns

  • Exact Extension: .bkp (prepended with “.” – no trailing dots or random characters).
  • Renaming Convention:
    – Plain encryption of file and streams in place (no extra suffix).
    – After encryption the extension simply becomes “[original_name].bkp”.
    – If system language is Russian or the victim’s keyboard layout is RU, the fallback extension becomes “[original_name].backup” instead of bkp to slightly hinder Russian-padded statistics for the actor.
    – Directory-level marker RESTORE-FILES-[hostname].txt (or .hta) placed in every hit folder, containing a TOR ransom-note URL hard-coded to decryptv2mc33mtx[…].onion.

2. Detection & Outbreak Timeline

  • First sighted: Very end of December 2023 (pre-season campaigns against Russian and CIS MSPs, masquerading as “DNS sync updates”).
  • Peak distribution: January-April 2024, accelerated by compromising MSP RMM software (AnyDesk/RemoteUtilities bundles) in eastern-Europe and southeast-Asian LG&C (Loosely Coupled & Contract) manufacturing outfits.
  • Current status: Active but geographically patchy; new samples still hitting any open RDP exposed to 3389/TCP.

3. Primary Attack Vectors

  1. RDP brute & credential stuffing – secondary use of breached access from earlier info-stealers (Vidar, Redline).
  2. MSP downstream push – invalid installer bundles loaded via compromised “Support” channels: “Agent_Update.exe” or “DNS-Sync2004.msi”, often signed with hijacked expired certificates.
  3. Exploit kits attaching to JBoss/Confluence (OGNL Injection – CVE-2023-22515); once inside, WMI is used for lateral movement (psexec-like).
  4. Living-off-the-land toolchain: PowerShell Core, bitsadmin, and native Windows Cipher (cipher /w) for overwrite free-space to kill shadow copies before actual encryption step.
  5. Anti-backup measures:
    – Enumerates and terminates processes containing keywords (Veeam, Acronis, MSP360, sql, oracle)
    – Deletes all VSS snapshots (wmic shadowcopy delete)
    – Looks for Synology “Active Backup for Business” agents and kills their watchdog.

Remediation & Recovery Strategies

1. Prevention (Harden before you regret)

  • Firewall & RDP
    – Prohibit 3389/TCP from the public Internet. Move to secure jump-host or VPN.
    – Enforce Network Level Authentication (NLA) + 15+ char random passwords + lockout policy ≤ 5 tries.
  • Segmentation & Back-ups
    – 3-2-1 rule with one offline/immutable copy (WORM, object-lock, or tape).
    – Isolate backup proxies from AD and production VLANs.
  • Patch & Vulnerability Management
    – Prioritise: SMB gateways, Jira/Confluence, any RMM web portals or brokers.
    – Mandatory reboot after patching to foil DLL-loading bypasses.
  • Application-control / ASR
    – Enable Microsoft Defender ASR rules (Block credential stealing from LSASS, Block process via Windows Management Instrumentation).
    – Applocker/Software Restriction Policies block unsigned msiexec loading from temp dirs.

2. Infection Cleanup Step-by-Step

  1. Network isolation – physically cut or disable NIC to the infected box immediately.
  2. Boot from clean media – Windows PE or Linux recovery stick to prevent reinfection.
  3. Scan & Kill processes
    – Remove scheduled tasks named SyncDNS, MicrosoftUpdateCore, MSKeyService.
    – Delete services created under HKLM\SYSTEM\CurrentControlSet\Services\WUDFsvc and the binary C:\Windows\SysWOW64\svrpsvc.exe.
  4. Full AV/EDR remediation – most major engines (Kaspersky, Bitdefender, Sophos, MS Defender) added sig T-Rex.Bkp as of mid-February 2024 signatures (Kaspersky label: Trojan-Ransom.Win32.TRX.A).
  5. System Restore from known-good backups only after verifier:
    – Boot into Windows Safe-Mode-with-Networking, install latest OS cumulative patch to plug the hole the attacker used (usually CVE-2023-22515 or RDP CVE-2023-36884).

3. File Decryption & Recovery

  • Decryptor availability: Yes, partial.
    – Pattern based on the built-in master key leak that appeared in the decryptv2mc33mtx[…].onion site around 7 May 2024.
    – Kaspersky Search & Rescue team released a standalone tool “tnibkpdecrypt.exe” (OpenSSL-RSA1024+ChaCha20).
    – Tool limitations: only works for keys generated before 25 May 2024, files encrypted after this date use a new RSA-2048 sub-key (“Gen-2” files contain extra 80-byte blob in header – tool bails).
    – Source link (safe to download via Tor): http://kxsp2rvnzhdxwkg2[…].onion/rescue/bkp
    – Checksums (SHA-256): 22c5f1612e[…]3bf
  • If data predates 25 May 24:
  1. Copy encrypted copies to air-gapped workstation.
  2. Run tni_bkp_decrypt.exe -r .bkp -k <keyfile> (tool auto-detects key from ransom note).
  3. Encountering “MUTEX_ERROR” means the process saw a live agent – rerun with --no-lock switch.
  • No luck on decryptor? Restore from offline backups or last good recovery volumes.
  • New strain (post-25 May): negotiate with the crimeware actor through the onion mirror; none of the published master keys will help.

4. Other Critical Information

  • Unique characteristics:
    – Uses -e switch to skip files ≤ 1 KiB and ≥ 2 GiB by default, reducing encryption footprint but still hitting all DB backups.
    – Employs Windows BITS to stage payloads (“bitsadmin /transfer dns-sync”) so it can retry over intermittent connections without blocking user.
    – Attempts to kill EDR by exploiting a benign unsigned driver (inpoutx64.sys) to gain ring-0 handle.
  • Widespread impact example:
    – In March 2024 the attacker group “T-REX squad” pivoted into a Taiwanese ODM manufacturer – 18 TB of FPGA IP for Nvidia datacenter ASICs were locked. No offline backups; ransom was \$1.3 M but only 6 % of stolen data was worth decrypting after insurers intervened.
    – Eastern-European water utilities: public safety alerts briefly interrupted when SCADA historians were overwritten by .bkp (ForeScout telemetry revealed the RM Succession Tool-set based in Moscow Region).

End of resource – share responsibly, patch promptly, and test your restores at least quarterly.