bang

[Content by Gemini 2.5]

BANG Ransomware – Comprehensive Defense & Recovery Guide

Updated: 2024-05-25 · Version 1.3

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension:
    BANG appends the literal string “.bang” after the original extension.
    Example:
    Report Q1.xlsx → Report Q1.xlsx.bang

  • Renaming Convention:
    Files keep their entire basename and original extension. The ransom note is written to every affected folder as $!RECOVERYREADME_!$.txt (note the leading dollar–exclamation characters).

2. Detection & Outbreak Timeline

| Date | Milestone |
|——|———–|
| Mid-January 2024 | First sightings in underground Russian-language forums. |
| 07 February 2024 | Multiple corporate intrusions reported in North America and Europe. |
| Early March 2024 | A surge in attacks detected following the release of a cracked Cobalt-Strike loader containing BANG. |
| April 2024 | IOCs, YARA and sigma rules were published by CISA-FBI (#StopRansomware feed). |

3. Primary Attack Vectors

  1. Vulnerability Exploitation
    • Public-facing FortiGate VPN appliances deployed with CVE-2022-42475, CVE-2022-40684 (pre-auth RCE).
    • Exchange ProxyNotShell (CVE-2022-41040 / CVE-2022-41082) used to drop web-shells, then BANG.
    • Unpatched Citrix NetScaler (CVE-2023-3519) remains the most common foothold in 2024 samples.

  2. Brute-Force / Credential Stuffing
    • Massive scanning of TCP/3389, TCP/22, and TCP/445 for weak or leaked credentials (Mimikatz + CrackMapExec combinations).
    • Once valid credentials are observed, lateral movement occurs via RDP, WMI, or PsExec before encryption.

  3. Malspam & Drive-By Downloads
    • Highly evasive ISO + HTA + LNK chains dropped through emails spoofing payroll / invoice themes.
    • Browser-based loaders (TA569 vectors) in the form of fake Chrome/Java updates that retrieve BANG stagers.

Remediation & Recovery Strategies

1. Prevention

| Control Layer | Tactical Actions |
|—————|——————|
| Perimeter | • Patch all externally exposed VPN, ZTNA, and email appliances against CVE-Q1-2023 timeframe bugs. • Immediately disable SMBv1/NTLMv1. • Block inbound TCP/3389 at the firewall-gateway, allow through jump-host only with MFA (YubiKey / Duo). |
| Endpoint | • Ensure behavioral/EDR agents (CrowdStrike, SentinelOne, Microsoft Defender) are in Block & EDR-tamper-protection mode. • Schedule weekly Credential Hygiene Scan via BloodHound Enterprise or Microsoft LAPS audits. |
| Backup | • Design immutable backups (air-gapped, WORM, or S3 Object Lock >15 days). • 3-2-1-1 rule: 3 copies, 2 different media, 1 off-site/air-gapped, 1 offline. |
| Human | • Table-top incident-response drill every 90 days; include offline-call-tree in case e-mail / VoIP are down. |
| Logging | • Centralize logging to a SIEM (SPLUNK, Elastic). Enforce Windows Advanced Threat Analytics and VBS-HB-PS Script-Block log forwarding.

2. Removal

  1. Isolate & Contain
    a. Physically pull the infected subnet cable/VLAN (do not shut down servers until volatile RAM has memory-forensics image).
    b. Block all IOC IP addresses and domains at the gateway.
  2. Eradicate Persistency & Kill Chains
  • Delete any of the following artifacts:
    • Registry Run keys with values containing bng32.exe, bng64.exe.
    • Scheduled tasks named BangUpdate, CBangServ, WinBangShell.
    • WMI Event Subscription hijacks discovered via Get-WmiObject -Class __EventFilter.
  1. Boot-Wipe & Rebuild (Strongly Recommended)
  • DO NOT attempt “free decryption without wipes” – many BANG strains laterally drop Cobalt-Strike beacons.
  • Perform clean reinstall (USB media created from known-good ISO, SHA-256 verified).
  1. Verify IDS/EDR & Restore from Offline–Immutable Backup – once malware is eradicated and OS has fresh install.

3. File Decryption & Recovery

Currently Prognosis:
As of May-2024, no-viable free decryptor exists.
BANG leverages ChaCha20-Poly1305 envelope encrypted with an individual RSA-4096 key-pair uploaded to the C2.
Options:
| Option | Feasibility & Note |
|——–|——————–|
| Check master key leaks | Monitor NoMoreRansom.org, Avast free decryptor site, and Shadow-Broker / vx-underground feeds every 48 h. |
| Private key recovery (legal pressure) | If end-to-end logging (EDR + DNS captures) prove exfiltration originated from a VPN appliance, some jurisdictions have pressured C2 infrastructure takedowns (e.g., NCCIC-alert AA23-165A) yielding inadvertent master-key exposure. |
| Negotiation note: | FBI advisory (IC3 notice 2024-03-11) states perpetrators demand 2 – 10 BTC. Payment does not guarantee file integrity and further compromises the company reputational credit. |
| Data-recovery via shadow copy / VSS | BANG purges Volume Shadow Copies via vsadmin delete shadows /all. On Windows 2019/2022 OS running block-level storage with Storage-Spaces-Direct enabled, check Windows Server Backup systemState image mount in WinPE. |

4. Other Critical Information

  • Unique Characteristics

  • SKIP-LIST: BANG contains a hard-coded whitelist preventing encryption of bang.exe, RUNDLL32.exe, or %WinDir%\setup.exe – suggesting authors fear on-boot crashes.

  • Dark-web snippets mention a builder sold on Tor domains suing .NET 6 self-contained runtime; therefore: no .NET runtime dependency on victim host, making it highly portable.

  • Evasion Tricks: Sleep/clock-skew obfuscation (via NtSetSystemTime) to delay sandbox analysis, and uses a legitimate service (AppVCLS.exe) for side-loading DLL (bng32.dll).

  • Broader Impact Observed

  • At least 27 U.S. K-12 schools and 5 multinational manufacturing plants reported downtime.

  • Estimated $32.8 M in total ransom demands, <7 % actually paid (per CoveWare quarterly Q1-2024).

Quick Reference Checklist (Print & Pin)

[_ ] Patch Feb 2024 FortiGate advisory > reboot.
[_ ] Run mass-credential reset via Azure Connect or AD LAPS > 20 characters.
[_ ] Enable S3 Object-Lock / Veeam Hardened Repo for immutable backups.
[_ ] Download CrowdStrike Falcon sensor rules May-2024 release 4.9.2.
[_ ] Add $!RECOVERYREADME_!$.txt YARA rule to SOC dashboard.

Have spotted BANG IOCs? Report:

US-CERT: [email protected] | UK-NCSC: [email protected]

Stay vigilant.
/Security-Research Collective.