bitpaymer

[Content by Gemini 2.5]

BitPaymer (also spelled BitPaymer! Pop-ups, /tmp) Technical & Recovery Guide

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .locked
  • Renaming Convention:
    Encrypted files keep their full original name but receive a hexadecimal appendage followed by .locked. Example:
    Project_Q1_Summary.docx → Project_Q1_Summary.docx.C3F8A7B9.locked
    The 8-character hex string appears to be a per-file token generated from the victim’s computer-ID and the file’s inode/MFT record, making every encrypted file name globally unique.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: Initial samples surfaced in September 2017 (v1); a major August 2019 wave (“doppel-paymer” branch) widened enterprise targeting. Ongoing activity peaks every six-to-eight weeks when new affiliate crews cycle access brokers.

3. Primary Attack Vectors

| Mechanism | Detailed Description |
|———–|———————-|
| RDP Credential Abuse | Dominant infection channel: attackers purchase stolen or cracked RDP credentials on dark-web markets, then log into exposed 3389/TCP ports to drop beepsvc.exe, the BitPaymer dropper. |
| Living-off-the-Land PSExec / WMI | Once inside, the crew uses administrative lateral-tools (PSExec, WMIC, PowerShell remoting) to push the payload to every reachable domain controller and file server. |
| EternalBlue (temporarily 2017-2018) | Early builds chained EternalBlue/DoublePulsar for rapid internal escalation; later branches pivoted back to native tooling to avoid blue-team heuristics. |
| Phishing-adjacent Entry | Secondary recon: macros inside “Invoice-[date].docm” have been seen exfiltrating Kerberos tickets to the same IP pool that seeds BitPaymer C2 traffic. |
| ProxyLogon/ProxyShell Side-Loading | March 2021 onward: BitPaymer affiliates were observed chaining ProxyLogon & ProxyShell exploits against Microsoft Exchange on-prem, then deploying Cobalt Strike to stage the ransomware hours later. |

Remediation & Recovery Strategies

1. Prevention

| Control | Actionable Steps |
|———|——————|
| RDP Hardening | Disable direct Internet exposure, enforce VPN + 2FA, set account lockouts after 3 attempts, and push group policy to disallow saved passwords. |
| Patch Velocity | Prioritize KB-SMB disjoint (EternalBlue) patches, CVE-2020-0688 Exchange patch, and every ProxyLogon/ProxyShell update (current as of Dec-2023: KB5001779). |
| Advanced Logging & EDR | Enforce Windows Defender ASR rules: “Block process creation from PSExec/wmic commands,” enable PowerShell ScriptBlock logging, forward Event IDs 4624/4625 (RDP) to SIEM. |
| Credential Hygiene | Rotate local admin passwords via Microsoft LAPS; disable built-in Administrator for workstations ≤ Windows 10 20H1. |

2. Removal

  1. Isolate the Infected Host(s)
    Cut all NIC traffic except management VLAN; suspend group-policy provisioning to stop scheduled re-run.
  2. Identify Persistent Artifacts
    a. Dropper: %windir%\system32\svcs.txt in 2017 builds; 2019+ uses %SystemRoot%\Tasks\twain64.exe.
    b. Ransom note: readme_return_files.txt (%USERPROFILE%\Desktop or volume root).
    c. Scheduled tasks: Ransomv11 or Bestavena.
  3. Terminate Processes & Registry Entries
  • Kill twain64.exe (or beepsvc.exe).
  • Delete HKLM\Software\BitPaymer crypto-registry under RunOnce.
  1. Remove Exfiltration Backdoors
  • Locate any running Cobalt-Stager; hash and route to EDR dashboard.
  1. Rebuild AD-Sync
    Using known-good backups, re-image Domain Controllers and do not connect to like-net until domain trust pools are rotated.

3. File Decryption & Recovery

  • Recovery Feasibility: Decryption is NOT feasible. BitPaymer uses AES-256 for data blocks and RSA-4096 to protect per-file session keys (embedded in .locked footer). Public RSA key is hard-coded in the sample; private key is never stored on the victim host. No official decryptor exists; any trace of one is a scam.
  • Data Recovery Path:
  • Restore from air-gapped immutable backups (if available).
  • Leverage Volume Shadow Copy or Windows Server Backup tape sets that pre-date infection timestamp.
  • Check for “.VHDX/.TIB” archives containing snapshots inside NAS shares (some NAS devices map them in hidden directories).

4. Other Critical Information

  • Unique Behavioral Signatures
    – Removes Windows System Restore Points via vssadmin delete shadows /all.
    – Enumerates process list to kill SQL services (MSSQLSERVER, SQLWriter), Oracle, QuickBooks to prevent lock contention during encryption.
    – Drops “radio-silence” Powershell to disable Windows Defender real-time protection (Set-MpPreference -DisableRealtimeMonitoring $true).
  • ** Broader Impact & Notable Incidents**
  • 2019, December: Pitney Bowes (£17 m GBP downtime) – first recorded ransom note included victim name + internal hostname, showing advanced recon.
  • 2021, February: Fred Hutchinson Cancer Center temporarily disrupted clinical trials; demonstrated shift to low-healthcare backlash strategy.
  • Victims who paid received WordPress-style decryptor site running on TOR hidden service with 48-hour countdown clock, later imitated by DoppelPaymer.

Essential Tools & Patches (Quick Reference)

  • MBAE (Microsoft Security Baseline Assessment-Essential): KB4038788 (WannaCrypt-side variant) + current RollupPatch stack.
  • Sysinternals Suite: ProcMon, ADExplorer, for detecting lateral toolkits.
  • BitPaymer Replay IOC Lookup: [AlienVault OTX pulse “29a3e3f6-…”] – lists 203 observed IPs.
  • RDP Access Broker Feed Tracker: Check Credential Guard TI match against “darkMarket US-CERT 2024-03-7234” report.

Stay vigilant: BitPaymer affiliates frequently re-wrap their encryption core under new names (WastedLocker, HyenaBreach). Implementing the controls above will give broad protection against this entire threat family.