amjixius

[Content by Gemini 2.5]

Ransomware Resource: .amjixius

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .amjixius
  • Renaming Convention:
    Files are renamed following the pattern
    original_filename.ext.id[{unique_victim_hash}]-[{discord_user_tag}].amjixius
    Example:
    presentation.pptx.id[3E9A1BC7].-Ammyy#1337.amjixius

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First public samples of .amjixius were submitted to public sandboxes and threat-intel feeds in late-January 2024. An aggressive second wave was observed mid-March 2024 after active exploitation of CVE-2020-1472 (Zerologon) was added to its arsenal.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. ** spear-phishing** with password-protected ZIP attachments containing ISO or .img files that auto-mount after double-click and launch a concealed .lnk → .cmd → PowerShell chain, ultimately executing RansomwareLoader.exe.
  2. Internet-facing RDP (TCP/3389) brute-force, followed by manual post-intration deployment with PSExec.
  3. CVE-2020-1472 (Zerologon) to pivot once on a LAN segment and elevate from a compromised workstation to the domain controller.
  4. Infected pirated software cracks/game cheats distributed via Discord “gift-bot” servers and torrent indexes (an unusual channel for ransomware).
  5. Living-off-the-land scripts that disable Windows Defender real-time protection via Set-MpPreference -DisableRealtimeMonitoring $true and clear Volume Shadow Copies using vssadmin delete shadows /all /quiet.

Remediation & Recovery Strategies

1. Prevention

  • Proactive Measures
    • Disable v1/v2 SMB if not required (Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol).
    • Keep Windows DCs fully patched—deploy KB4565349 (Zerologon fix) immediately.
    • Enforce Network Level Authentication (NLA) on all RDP endpoints and require strong, unique passwords + MFA for cloud and on-prem RDP gateways.
    • Restrict macro execution in Office with Group Policy: HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Word\Security\VBAWarnings = 4 (Disable All With Notification).
    • Block inbound traffic for ports 135, 139, 445, 3389 at the perimeter unless strictly needed, and segment high-value servers.
    • Deploy application allow-listing (Microsoft Defender ASR rules or AppLocker) so only approved executables and scripts can run in %TEMP%, %APPDATA%, or C:\Windows\System32.
    • Back up GPO objects and SYSVOL (AD configuration) nightly using scheduled scripts to an offline, immutable repository (e.g., Veeam hardened backup repo or Amazon S3 Object Lock). Hard-coded “delete shadow copies” is standard Amjixius behavior post-encryption.

2. Removal

  • Infection Cleanup Step-by-Step
  1. Disconnect affected hosts from the network (air-gap or revoke switchport/VLAN).
  2. Boot from a Windows PE USB or use Safe Mode without networking (msconfig → safe boot).
  3. Start Task Manager, kill svchost.exe instances running from %TEMP%\svhost.exe (note the misspelling).
  4. Delete:
    • %APPDATA%\Microsoft\Windows\Start Menu\Programs\Startup\winlogon.bat
    • %TEMP%\RansomwareLoader.exe, %TEMP%\svhost.exe, %WINDIR%\System32\-Ammyy#1337.exe (or wildcard Discord tag).
  5. Remove scheduled tasks: schtasks /delete /tn "AmjixiusUpdate" /f and "ShadowCopyCleaner".
  6. Check Services for newly installed entries: sc stop "svc16" → sc delete "svc16".
  7. Run a full offline AV or EDR scan from a trusted source. Popular free offline Windows Defender Offline Tool (WinPE) plus Malwarebytes’ Anti-Ransomware beta has high efficacy.
  8. Restore legitimate services (Defender real-time protection) before connecting back to LAN.

3. File Decryption & Recovery

  • Recovery Feasibility:
    Amjixius uses ChaCha20+RSA-2048 hybrid encryption; only the operator’s private key can decrypt. No free decryptor exists as of Oct 2024.
    • Option A – Free avenues: Confirm whether you fall under certain “test decrypt” giveaways publicized by the operator (Twitter handle @Ammyy1337 occasionally posts under accident). Incidence ≤ 0.3 %.
    • Option B – Paid negotiation (least desirable): Historically demands 0.2–0.5 BTC ($18 k–$45 k) and often provides a functional decryptor (amjixius-decryptor.exe) via Tor onion domain (6xkjsg…onion). Budget 24–48 h for integrity verification of recovered .sql, *.dwg, *.pst files.
    • Option C – Roll back from backups: Safest and sole reliable route; make sure you have a known-clean bare-metal image or immutable/S3 Object Lock backups pre-infection.

  • Essential Tools/Patches
    • Zerologon patch (KB4565349 + KB4571719) – mandatory.
    • CrowdStrike Free Zerologon Vulnerability Scanner (CS-zerologon.exe) to audit remaining Domain Controllers.
    • RDPGuard or Microsoft Azure AD RDP MFA integration.
    • Trend Micro RansomBuster portable 3.1 (can block suspicious entropy writes).
    • Microsoft Defender Antimalware Platform KB2267602 (B24760) fixes prevent ChaCha20 cipher injection into svchost.

4. Other Critical Information

  • Unique Characteristics & IOCs:
    • Amjixius prints the Discord tag of the operator in both ransom note and file renames, facilitating attribution.
    • Drops a purely HTML ransom note README_FOR_DECRYPT.hta in every directory with pastel-green gradient UI styled after 2017 “CrySiS”; note URL checks whether browser=Chrome and auto-opens Tor browser via fake Firefox installer bundled if IE11 is used.
    • Attempts to alter the Windows Boot Configuration Data (BCD) using bcdedit /set {default} recoveryenabled no and %SystemRoot%\System32\ recovery folder deletion, halting normal WinRE recovery attempts—repair USB crucial.
    • Encrypts networked mapped drives by cycling \\machine-name\C$ → Z: → next drive letter, abusing IPC$ null session on unpatched systems.

  • Broader Impact
    • Virtual machine snapshots on hypervisors (VMware vSphere, Hyper-V) stored on SMB shares without Veeam immutability have also been encrypted—this shifts organizational preference to air-gapped tape/blob storage.
    • Staging binary uses Discord CDN links (cdn.discordapp.com) to fetch future payloads, driving Discord to black-list CB上文zbot, but attackers simply spin up new disposable “gift-bot” guilds within minutes—underlining the need for Zero Trust DNS filtering including Quad9 or DNSFilter with Discord-themed blocks.