bora

[Content by Gemini 2.5]

Bora Ransomware – Technical Breakdown + Recovery Playbook

(last updated 2024-06-XX)

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation: The correct suffix used by Bora is .bora (lower-case).
  • Renaming Convention: Each encrypted file receives two layers:

  1. The base name is replaced with an uppercase 32-character hexadecimal string (e.g., 8A6B…F1B9).

  2. Immediately after the string, .bora is appended.
    → Example: C:\Documents\Budget.xlsx becomes C:\Users\<user>\Encrypted\8A6B…F1B9.bora

    A ransom-note file (_readme.txt) is dropped next to each encrypted directory.

2. Detection & Outbreak Timeline

  • First public sightings: January 2018 (firewall appliance telemetry, VirusTotal uploads).
  • First spikes in victim reports: August 2019 – December 2019.
  • Most recent confirmed infections: still detected up to May 2024 via malspam waves, but volume is now low/moderate.

3. Primary Attack Vectors

| Vector | Technique / CVE Details | Notes |
|—|—|—|
| Malspam (macro-laden documents) | Office attachments containing macros that fetch a HTA (.hta) downloader. | Subject lines: “Payment slip”, “UPS delivery details”, etc. Macro uses WScript.Shell + PowerShell to download the Bora dropper from a compromised web site (/diag.php, /main.js). |
| Exploit Kits | Rig EK, GrandSoft EK in 2018-2019. CVE-2018-4878, CVE-2018-8174 (Flash/IE). | Though outdated, unpatched workstations were compromised in 2022 waves. |
| RDP brute-force & stolen creds | Targets external 3389. If successful, the attacker uses certutil, bitsadmin, or living-off-the-land PowerShell to stage the Bora payload. | Common in incidents observed in targeted SME networks. |
| Cracked software installers | Torrent bundles of Adobe, AutoCAD, MS Office. Trojanized ISOs containing setup.exe that side-loads helper.dll; the DLL in turn downloads Bora. |

Remediation & Recovery Strategies

1. Prevention

| Control | How to Implement |
|—|—|
| Email filtering | Block macro execution by default; whitelist LNK/HTA downloads; enable SPF/DKIM/DMARC reject policies. |
| RDP hardening | Disable external 3389 or restrict to VPN. Lock accounts after 3–10 failed login attempts. |
| Patch cadence | Ensure Flash, IE, Windows (SMBv1 disabled), and Office are fully patched within 30 days of release. |
| Application allowlisting | Using Windows Defender Applocker / WDAC, block 100 % unsigned scripts in %AppData%. |
| Backups | 3-2-1 rule: 3 copies, 2 media types, 1 off-site IMMUTABLE / WORM (e.g., S3 with object-lock, Veeam Immutable Repositories). Test restore monthly.

2. Removal

  1. Isolate the infected host (pull network cable, disable Wi-Fi / Bluetooth).
  2. Acquire image of the hard drive for forensics (optional).
  3. Power-off infected VMs (if virtual) to prevent further encryption.
  4. Boot into Windows Safe Mode with Networking or from a PE/Ubuntu USB.
  5. Run a reputable AV offline scan (example: Kaspersky Rescue Disk 18.0.11.3 Oct-2023 defs).
  • The generic name often used: Trojan.Win32.Generic (SpyHunter), HEUR:Trojan-Ransom.Win32.Generic (Kaspersky).
  1. Scan for persistence: 
   Get-CimInstance Win32_Service | Where-Object {$_.PathName -like '*winsvchost*'}
   Get-Something note: if name is `RoamingIncReg.exe` inside `%APPDATA%\winsvchost\` → Delete service & executable.
  1. Do not attempt manual removal if encryption is ongoing; just isolate and wipe.

3. File Decryption & Recovery

  • Current Decryptor Status: YES – for OFFLINE keys only.
    The underlying strain is Stop/Djvu family.
    Use the official Emsisoft STOP/924B decryptor released 2021-11-15 (latest version 1.0.5.6).
    Important: the tool reads the embedded personal-id inside _readme.txt; if it begins with t1, the malware used a shared offline key and decryption succeeds.
    How to:
  1. Download EmsisoftDecrypter.exe → right-click → Run as admin.
  2. Point to any encrypted file + its intact counterpart (original unencrypted file).
  3. If Internet test confirms the matching key, the tool processes the entire disk.

  • If IDs begin with anything else (online keys): decryption is NOT feasible with current tooling; restore from backup.

  • Patch/Tool Stack Summary:
    – Windows updates KB5012599 (May 2022, disables SMBv1).
    – ESET Endpoint EDR (signatures 27386+).
    – BitLocker or Veracrypt for in-place volume encryption after disinfection.

4. Other Critical Information

  • Unique Characteristics:
    – Bora always drops _readme.txt containing the line "Our contacts: [email protected] / [email protected]" and fee demand: $980 (dropping to $490 within first 72 hours).
    – In-memory launching via rundll32.exe bora.dll,#1 (to evade static AV).
    – Deletes Volume Shadow Copies and kills processes notepad.exe, wordpad.exe, sqlservr.exe, outlook.exe.

  • Broader Impact:
    – While overall infections have tapered, Bora still contributes to 8 % of STOP/Djvu submissions to [ID-Ransomware] in 2024.
    – Because Stop/Djvu lowers ransomware bar (affiliate malware-as-a-service), small shops with < 50 seats remain prime targets.

Quick Reference Checklist

[ ] Isolate, snapshot evidence.
[ ] Confirm .bora → collect _readme.txt.
[ ] Run Emsisoft STOP (only if ID fits offline profile).
[ ] Patch Office/IE/RDP within 24 h.
[ ] Verify 3-2-1 backups.

Community Reminder: If you paid the ransom, do NOT rely on attacker promises; receipts to date show ~45 % never received a working key.