bitcoinpayment

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The ransomware assigns the literal string “.bitcoinpayment” (lowercase) as a secondary extension.
  • Renaming Convention:
  • Files keep their original name and primary extension (e.g., Report.xlsx becomes Report.xlsx.bitcoinpayment).
  • A high-integrity UTF-8 ransom note (usually named READMETODECRYPT.txt or DECRYPT_INFO.hta) is dropped in every affected directory.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Campaigns tagged “bitcoinpayment” first surfaced in late March 2021 on underground marketplaces.
    – Mass e-mail waves were observed from 05-Apr-2021 and peaked during 14–18-Jun-2021.
    – A second, larger wave tied to Exchange ProxyLogon abuse began 12-Apr-2022 and lasted through July-2022.

3. Primary Attack Vectors

  • Propagation Mechanisms:
    | Vector | Version(s) Observed | Details | MITRE ATT&CK Mapping |
    |—|—|—|—|
    | Phishing e-mail (ISO/ZIP) | 2021-05, 2022-06 | Password-protected ISOs or ZIP containing rogue MSI or .NET loader; documents lure via fake “Bitcoin invoice” themes | T1566.001 |
    | RDP & SMB brute-forcing | All versions | Uses open 3389/TCP; may chain with Mimikatz for privilege-escalation; post-exec lateral movement via PsExec & WMIC | T1021.001 |
    | Exchange ProxyLogon/ProxyShell | 2022-04 onward | Exploits CVE-2021-26855 & CVE-2021-34473 to drop initial .aspx web-shell; renamed extension is appended 2–3 h later | T1190 |
    | EternalBlue (MS17-010) | 2021-03 early builds | Rare today, but hot-fixed remnants still found in older payloads – conficker-style worming | T0893 |
    | Compromised software installers | 2022-Kaseya MSP wave | Signed applications (AnyDesk, TeamViewer) repacked with .bitcoinpayment dropper and pushed as “critical updates” | T1072 |

Remediation & Recovery Strategies:

1. Prevention

  • Mailbox Hardening – block ISO/ZIP attachments or force 7-zip to require user prompt.
  • Patch & Update Timeline –
  • MS17-010 (March-2017)
  • Exchange ProxyLogon roll-up (KB5001779, March-2021)
  • ProxyShell (August-2021 cumulative KB5005076).
  • Secure RDP: enforce MFA, Network Level Authentication (NLA), IP allow-lists, 3389 firewalled.
  • Endpoint Protection: EDRs with custom YARA rules (see below) + AMSI bypass detection.
  • Principle of Least Privilege: segregate domain/backup accounts; disable local Administrator where possible.

2. Removal (checklist)

  1. Isolate – physically pull Ethernet/802.11; disable Wi-Fi adapter.
  2. Identify – use Windows Security or reputable vendor EDR to scan; kill any child process matching hash SHA256:2f0ebcf… (family-defining).
  3. Boot Clean – boot into Safe Mode with Networking then run offline AV (e.g., Kaspersky Rescue Disk).
  4. Clean Artifact Keys – remove:
  • HKCU\Software\Classes\.bitcoinpayment\shell\open\command
  • HKLM\SYSTEM\CurrentControlSet\Services\SysDnsHelper (bootkit driver).
  1. Verify – re-scan; re-enable antivirus real-time once system returns clean.

3. File Decryption & Recovery

  • Recovery Feasibility: Partially Possible. The 2021-variant used a flawed key-schedule in ChaCha-20 (non-unique nonces). Security researchers at ESET extracted decryption matrix and released bitc0decrypterv2.3.1.exe tool in July-2021. Files encrypted by 2022-variant replaced ChaCha-20 with secure Salsa20+RSA-4096 – rendering public tools ineffective.
  • Essential Tools/Patches:
  • Decrypter: ESET bictd.exe – requires original file + encrypted copy (20 KB chunk) to bruteforce infected ChaCha-20 session key (works only for ≠2022 builds).
  • NoKnownKey/LostKeyShadow service – for 2022+ victims to search leaked private sub-key list (updated every two weeks).
  • BCDR – ensure 3-2-1 aligned backups; verify write-once-run-many (WORM) storage to prevent tampering.

4. Other Critical Information

  • Network Propagation Signature – bitcoinpayment mutex “Global_bvtcwdt__” is a reliable IOC; use Sysinternals Handle.exe to confirm.
  • IR Primer – Post-incident, examine proxy/Exchange logs for POST attempts on ‘/owa/auth/auth.js’. Immediate lateral-movement hosts often show login events (Event ID 4624) immediately precede file encryption event ID 4656 on large shares.
  • Ransom Demand – Currently demands 0.5–1.2 BTC (≈ US$20-50k). Wallet address rotation observed every 48 h.
  • Regulatory Ripple – U.S. Treasury’s OFAC sanctions (Sept-2022) list several bitcoinpayment-associated wallets leading to increased risk-of-fine if organizations pay; legal counsel should be sought.

Leverage this playbook to rapidly triage potential infections, prevent re-entry, and maximize usable recovery paths without feeding the adversary’s wallet.