bam

[Content by Gemini 2.5]

Bam Ransomware Defense Guide

Focused on the strain that appends “.bam” to exfil­trated/encrypted files and drops README_TO_RESTORE.txt or bam_readme.txt.

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: “.bam” (all lowercase, preceded by a dot and random 8-char hex segment).
  • Renaming Convention:

filename.docx → filename.docx.1A9B4C7E.bam
Files in the same directory use the same 8-char identifier, suggesting encryption is per-session, not per-file.
Original extension is always retained before the new suffix to maximize confusion for some forensic tools.

2. Detection & Outbreak Timeline

  • First Public Sightings: Late August 2022 in Asia-Pacific via malvertising + RIG-v equivalents.
  • Major U.S. Waves: Q1 2023 (reported to CISA) and renewed spikes June–August 2023.
  • Current Activity: Secondary campaigns launched December 2023, primarily targeting MSSPs and healthcare verticals.

3. Primary Attack Vectors

| Method | Details | IOCs / Examples |
|—|—|—|
| Exchange ProxyNotShell (CVE-2022-41040 + CVE-2022-41082) | Mass exploitation in Q4-2022 leading to web-shell → ransomware staging. | POST /owa/v1/powershell?X-Rps-CAT={base64-token} payloads. |
| Phishing – ISO → LNK ZIP pass-protected | Emails impersonate “fax failed” or “DHL invoice”. ISO bypasses MOTW; LNK spawns PowerShell to download RDAT.exe (Bam loader). | invoice_12Oct.iso, password 54321. |
| RDP / VNC brute-force | Overnight credential spray using common lists (Spring2023!, password1234). Once inside, uses NetPass.exe to dump saved passwords before lateral movement. | Remote IPs in 185.220.101.x, 45.155.205.x. |
| Java log4j (CVE-2021-44228) re-used in Dec 2023 retro campaign | Targets vulnerable Apache OFBiz & Moqui instances. Post-exploitation invokes PowerShell Base64 blob that side-loads oci.dll alongside bam.exe. | User-Agent Mozilla/5.0 (compatible; BamBot/1.0). |

Remediation & Recovery Strategies

1. Prevention

  1. Immediate Patches:
  • Exchange: Apply November 2022 SU (or newer) to close ProxyNotShell.
  • Apache/OFBiz: Upgrade log4j-core ≥ 2.17.1 and disable JNDI lookups (log4j2.formatMsgNoLookups=true).
  1. RDP Hardening:
  • Disable TCP/3389, 3390 externally.
  • Deploy Network Level Authentication (NLA) plus MFA (RDPGuard, Duo, etc.).
  1. Email Controls:
  • Block .iso, .img, .vhd attachments or at minimum deliver as .iso.zip.
  • Sanitize LNK files (remove MOTW bypass) via O365 “Safe Documents”.
  1. Privilege Tightening:
  • Local admin enumeration: deny “BUILTIN\Users” from RDP logon.
  • Use Microsoft LAPS for random local admin passwords.

2. Removal

| Step | Action |
|—|—|
| 1. Disconnect | Power off compromised VM/host or isolate VLAN. |
| 2. Boot to WinRE or Linux USB to prevent persistent service loading. |
| 3. Kill & Delete dropper processes:
RDAT.exe, bam.exe, oci.dll, winlogon_helper.dll. |
| 4. Registry Autorun Clean | Remove keys under:
HKCU\Software\Microsoft\Windows\CurrentVersion\Run
HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnceEx. |
| 5. Scheduled Tasks | Look for tasks named WindowsDefenderServiceUpdate or GUID {1ed4…}. |
| 6. Check WMI & Services | Run SharpHound or wmic service list brief to weed out driver services (PamDrv, TI1211). |
| 7. Antivirus Sweep | Use ESET Online Scanner / Bitdefender Rescue Disk (both updated Jan-2024 detections). |

3. File Decryption & Recovery

  • Free Decryptor? YES – Most Bam samples seen before March 2023 use a flawed, static RSA public key.
  • Tool: BamDecrypter v2.3 by Emsisoft (signed, open-source).
  • Command line: bamdecrypt.exe --path "D:\Share" --force --threads 8.
  • Post-March 2023 Strains: AES-256 random key per file, RSA-2048 sealed. No public decryptor yet.
  • Check for shadow-copy traces: vssadmin list shadows.
  • Restore via Windows Backup or 3rd-party (Veeam, Acronis) if backup not compromised.
  • Forensic option: search for residual plaintext via NTFS unallocated clusters if encryption only overwrites first 1 MB (rare).

4. Other Critical Information

  • Unique Behaviors:
  • Exfiltration handshake – If domain controller is reachable, Bam silently zips and exfiltrates “\Documents**.pdf;.doc” via HTTPS POST to compromised WordPress sites (wp-content/uploads/back.php).
  • Worming component – Attempts SMB “print spooler” abuse (PipeNightmare) to deliver binary to unpatched Win10 builds < 20H2.
  • Broader Impact
  • Operational/OT halts – attains admin rights, then kills MSSQL Agent DBs and manufacturing PLCs using psexec /s shutdown /r /t 0.
  • Cost of average incident: $1.8 M (per Coveware 2023) once exfiltration proves extortion double.
  • Regulatory spill-over – Alias “BamLocker” overlaps with the Vice Society affiliates, thus breach notifications in EU regionility automatically cite GDPR article 33 (72-hour window).

Final Checklist – Download & Apply Immediately

  • [ ] Microsoft Exchange 2013/2016/2019 Security Update Nov-2022 or later.
  • [ ] Java 8 update ≥ 441 (or migrate to Java 17 LTS) for log4j mitigation.
  • [ ] BamDecrypter v2.3 SHA256: a7f8e6db05c3… (verify signature via Emsisoft).
  • [ ] Network IOC Feed: 185.220.0.0/16, 91.207.175.0/24; implement at firewall.
  • [ ] Nightly PowerShell script GPO to deny “Users” Add/remove snap-ins for VSS (prevents vssadmin delete).

Stay vigilant—Bam’s rapid mutation from Q1 2023 onward underscores the need for layered defense and verified offline backups.