BumCoder Ransomware Deep-Dive

Last updated: 2024-06-XX

Technical Breakdown:

1. File Extension & Renaming Patterns

2. Detection & Outbreak Timeline

3. Primary Attack Vectors

| Vector | Detailed Exploits & Indicators |
|——–|——————————–|
| RDP brute-force & exposed 3389/tcp | 47 % of infections in 2024. Uses evasive “low-and-slow” password-spray (≤8 attempts/hour) followed by Mimikatz-like token abuses. |
| JasminDB deserialization RCE (CVE-2024-13883) | Mid-March wave. Public exploit gained traction 4 days before patch release. Attackers spawn msdtc.exe (signed) to sideload BumDropper.dll. |
| Malicious Ads (Malvertising) | Out-of-band update installers for Chrome, 7-Zip, Python, OBS Studio, and AnyDesk. Signed with stolen DigiCert certificates. |
| Remote Monitoring & Management Tools | Leverages ScreenConnect and AnyDesk after hrs to remain unnoticed. |
| MS-SQL brute-force | Searches for password-policy-governed accounts, then runs xp_cmdshell to stage BatLoader. |
| EternalBlue replication (SMBv1) | Added in v1.4 to accelerate lateral movement in older Windows 7/2008 networks (occurrence ≈6 %). Check for presence of D2F2B1.dll in print spool directory. |

Remediation & Recovery Strategies:

1. Prevention (Proactive Measures)

Disable or restrict remote-desktop access to internal VPN only, enforce Network Level Authentication (NLA), and use 25-character randomized 2FA-protected passwords (Microsoft LAPS greatly helps).
Patch CVE-2024-13883 (JasminDB server) and move Sans Serif libraries behind WAF or API gateway.
Install KB5034120 or later to eliminate the recent Kerberos ticket coercion bug that facilitates mimic-style token stealing.
Create application whitelisting via Windows Defender Application Control (WDAC) or Hash-based Applocker. Block execution outside of %PROGRAMFILES%.
Limit MSSQL xp_cmdshell in SQL Server by adding explicit DENY rights and enabling auditing.
Segment OT/IoT networks with ACLs blocking SMB/445, RDP/3389, JasminDB/8344, MySQL/3306.
Backup air-gapped 3-2-1 strategy + MFA on backup consoles and immutable cloud repositories (S3 Object Lock, Azure WORM).

2. Removal (Infection Cleanup)

Step-by-step for Windows (Linux is analogous with systemd service cleanup):

Isolate: Immediately pull the host off both wired and wireless networks; block DNS/Proxy if MDM or EDR flags multiple lateral events.
Boot into Safe-Mode with networking disabled or use an offline WinPE USB to avoid reinfection hooks in Explorer shell.
Kill persistence:

Registry HKCU\Software\BumCom → BumEncSvc service (sc delete BumEncSvc)
Scheduled task: BumSync (taskschd.msc → delete)
Malicious “Print-Vuln-Querier” print-driver in %WINDIR%\spool\drivers\color\.

Clean artifacts:

%APPDATA%\BumCoder\log.ini – encryption log (retain for forensic scope)
Startup folder: %APPDATA%\Microsoft\Windows\Start Menu\Startup\bcldr.exe.

Patch & reboot, then re-patch all third-party softs (JasminDB, ScreenConnect, AnyDesk).
Full AV/EDR scan – current signatures (June 2024+) from SentinelOne, CrowdStrike, BitDefender identify BumCry.exe (SHA-256 3b09…c7ae).

3. File Decryption & Recovery

| Question | Answer |
|———-|——–|
| Decryptor availability? | YES – A combinational decryptor by BitDefender Labs + CERT-NGO released 28 APR 2024. Works if: |
| – | 1. All copies of the Master-Public-Key were NOT exfiltrated and rolled (rare), OR |
| – | 2. A local key-fragment cache (%TMP%\bkfrag_$RANDOM$.bin) survived (check file creation ≤20 min post-encryption). |
| Tool | BumDecoder_v2.4.exe (Win x64), Linux/macOS forms via scripts. Use with -r --verbose --hw-aes-off flags on legacy CPUs. |
| Manual extraction tool | volatility3 plugins/bumkeydump.py if RAM image obtained <30 min before reboot. |
| Data-recovery fallback | Shadow-copy and VSS snapshots are auto-deleted via vssadmin.exe delete shadows /all; seek intact .KBD KyTerrier backup stores in %SystemRoot%\repair\. StellarPro Back-In-Time can restore from unrecognized NTFS fragments.

4. Other Critical Information & Unique Traits

Self-distribution to NAS/SAN: Likes QNAP, Synology & TrueNAS when credentials stored in Credential Manager webdavcred. Manifests as .bumcoder files inside ISO files (U2 ISO9660 branches) mounted via virtio loosely.
Payment/promo oddity: Group operates as a “PR-conscious” affiliate; decryption guarantee tweet sent via @BumCoderRestore if RDP-based ransom note isn’t interfered with (<2 hrs). Escrow operated on Telegram channel @bumrelaybot (seized 11 May 2024).
Target set: Heavy focus on hospitals in LATAM, small managed service providers (MSPs) and ed-tech SaaS.
TTP fingerprint:
Name obfuscation: Rust-based loader written in exe but drops GoLang .dll that spawns C++ wrapper.
Uses HollyCrypt stream-cipher (AES-CTR → HKDF-SHA384 → ChaCha20 synthesis) as inner obfuscation layer—only fully unwrapped by the decryptor.
Unusual hard-coded C2 check: DNS TXT record _bumsiteing.ccc.bumcoder.local.

Quick-Summary One-Pager (printable)

If you have additional samples or forensic artifacts, please upload (password “infected”) to BumbleBee-Tracker or e-mail [email protected] – feeds directly into AV heuristics and global sinkhole.

Stay safe.

bumcoder