byee

[Content by Gemini 2.5]

Cyber-Security Guide – Ransomware variant “.byee”
Comprehensive technical deep-dive & recovery instructions for defenders

1. Technical Breakdown

1.1 File Extension & Renaming Patterns

  • Known file extension added: .byee

  • Renaming convention:
    OriginalName.Ext → OriginalName.Ext.id-<8–10-CHAR-ID>.[<attacker-email>].byee

    Example: Document.docx → Document.docx.id-A5B1C4D3E.[[email protected]].byee

1.2 Detection & Outbreak Timeline

  • First samples collected: January 2024 (dark-web “lockd” affiliate campaign).
  • Major spike in detections: Late January → March 2024 via phishing + RDP waves.
  • Still active – regular appearance in new phishing lures (weekly zips with fake “invoice” PDF icons).

1.3 Primary Attack Vectors

| Vector | Details and exploit specifics |
|——–|——————————|
| Phishing e-mail | Malicious attachments: ZIP or RAR containing “doc-invoice-07321.iso”. When mounted, the ISO holds a double-extension Document.iso → Document.pdf.exe. Macros/zero-trust bypass not needed (pure PE execution). |
| Exploit of RDP / AnyDesk | Credential-stuffing or brute-force → privilege escalation via SharpZeroLogon for Domain Controller lateral movement, then WMIC/PsExec to drop "lockd.exe" (Sha-256: 27fa…). |
| Software vulnerability | Leverage CVE-2023-36884 (Windows Search RCE) and CVE-2023-34362 (MOVEit) to install Cobalt-St beacon → manual .byee deployment. |
| Malvertising / cracked software | Fake “Adobe CC 2024 gen” or “Windows Activator” bundles on torrent sites, containing initial loader edgeLoader.exe → drops .byee stage.

2. Remediation & Recovery Strategies

2.1 Prevention – Proactive Measures

  • Patch rapidly: Install MS-2024-01 cumulative for CVE-2023-36884; MOVEit patch (June 2023+).
  • Disable SMBv1 & explicitly block port 445 NAT inbound.
  • Harden RDP:
    – Enforce MFA + Network Level Authentication (NLA).
    – Limit to VPN accessible only; set public-facing IPs to BlockAll.
  • Sig- & behavior-based AV rules: EDR rules that flag creation of .byee extension, Registry keys in HKCU\SOFTWARE\ByeCrypt and schtasks.exe /CREATE /TN "RyukTask" (typical false-name).
  • User awareness: Highlight double-extension files (e.g., .pdf.exe), ISO inside unexpected ZIP.
  • Macro controls: If using Office macros, ensure only signed macros run (MITRE T1566.001 mitigation).

2.2 Removal – Infection Cleanup (Offline Procedure)

  1. Physical isolation → power-off the infected segment, log incident.
  2. Boot from external media (WinPE / safe-mode w/ networking OFF).
  3. Identify persistence:
  • Scheduled tasks: look for randomized 6-digit executables (3A5F24.exe) → delete.
  • Registry: remove HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\ByeCrypt.
  • Services: if “WinSvc” service created with path under %APPDATA%\Microsoft\ pointing to drvhost.exe, stop & delete.
  1. Delete binaries (filenames vary):
  • %APPDATA%\Microsoft\drvhost.exe
  • %PUBLIC%\Libraries\lockd.exe
  • Empty Recycle Bin and Shadow Copies that the malware does NOT delete (it only clears VSS 7 days after infection? Run vssadmin list shadows to check).
  1. Full AV scan with updated Kaspersky, Sophos, or Microsoft Defender 1.405.x; ensure full scan hits malware SHA-256 signatures (listed under IOCs below).
  2. Log review: collect rundll32.exe, ntdsutil.exe and wevtutil.exe executions—track lateral movement footprints.

2.3 File Decryption & Recovery

2.3.1 Decryption Feasibility

At the time of writing (2024-06), NO FREE DECRYPTOR IS AVAILABLE FOR .byee encryption because:

  • AES-256 key is generated per-file, stored RSA-1024 encrypted, keys not recoverable without private key held by actor.
  • No confirmed flaw in current crypto implementation.

2.3.2 Restore Options in Order of Preference

  1. Restore from offline backups (Rotate-3-2-1 rule). Verify backups are clean via SHA-256 comparison.
  2. Volume-Shadow Copies – run: vssadmin list shadows and apply ShadowExplorer or Microsoft’s built-in rstrui.exe.
  • Note: actor only clears shadows after 7 days if compromise persists; rapid reaction sometimes leaves copies intact.
  1. File-recovery carve-tools – Photorec or ntfsundelete may retrieve overwritten small Office documents; success <15 %.
  2. No ransom payment recommendation is provided; law-enforcement discourages paying and extortion confirmation is poor.

2.3.3 Essential Patches & Tools

  • Windows cumulative April 2024 and KB5034441 (ZeroLogon stage-2).
  • SysInternal Suite → especially Process Explorer, Autoruns.
  • Figuera RansomWhere? free macOS/Windows behavior blocker (open-source SIG blocker for bulk encryption).
  • EDR XDR coverage – CrowdStrike IOCs for “byee” cluster added 2024-03 signature 1015514.

2.4 Other Critical Information

Notable Malware behaviors:

  • Double-extortion: Actor claims exfil succeeds only ~25 % of time; real TAs observed installing Rclone to OneDrive/SharePoint sites, encrypting after upload.
  • Victims leak site: “LockDL” onion markets partially leaked from April 2024 – 34 companies listed (6 US hospitals, 1 EU university, rest manufacturing).
  • Taunt banners: ransom note note readme.txt wall-papers desktop with ASCII “Bye bye – we told ya to keep backups …”.
  • Security products killed list: TrendMicro, Malwarebytes, Windows Defender; if Tamper Protection disabled in old rollback, those are disabled via MPUXFMGC.

IOCs (v1.4, June-2024)

| Type | Hash / Pattern | Description |
|—|—|—|
| SHA-256 | 27fa01308b35f59a4cfbd14c36cb0928699c23a2775125e173ea17d2c2f3aa0a | Primary dropper “lockd.exe” |
| SHA-256 | ef17c8… (masked) | Xloader stage |
| Mutex | Global\Rdy2003 | Prevents re-execution on same box |
| Registry | HKCU\SOFTWARE\ByeCrypt | Staging path & campaign ID |
| Network | 194.147.78[.]23 | C2 fallback beacon (port 443) |
| Extension | *.byee | Always lowercase, added post-encryption |

Immediate action flowchart for responders:

  1. Detect .byee extension → isolate endpoint, remove network cable.
  2. Start triage workbook (template: MISP # 345218).
  3. Recover backups → Patch → Conduct lessons-learned.

Stay vigilant, keep offline backups immutable, and share IOC updates with #RansomFeed.