aes_ni

[Content by Gemini 2.5]

────────────────────────────────────────
RANSOMWARE INTELLIGENCE BRIEF
File-Extension Variant: “.aes_ni”
────────────────────────────────────────

Technical Breakdown

1. File Extension & Renaming Patterns

  • File extension used: .aes_ni (lower-case, always preceded by a dot).
  • Renaming convention:
    – Original filename is preserved (e.g., Annual_Report.docx → Annual_Report.docx.aes_ni).
    – Full directory path is left intact (no folder-level extensions).
    – Some operators add a session-ID suffix like .aes_ni_x # where # is a small integer; the first drop is usually just .aes_ni.

2. Detection & Outbreak Timeline

  • First observed: Late Q4 2016 in Eastern-European malware-for-hire circles.
  • Widespread campaigns: Mass-spam delivery started January–February 2017; SMB-targeting variant detected February 2017.
  • Cluster-Lifetime: Heavy distribution ended Q3 2018; however, retro-variant binaries still surface in RaaS kits (ESXi encryptor discovered mid-2021).

3. Primary Attack Vectors

  1. Phishing e-mail → weaponised Microsoft Office macro or RTF exploiting CVE-2017-0199, CVE-2017-8570.
  2. Remote Desktop Protocol (RDP) compromise: brute-force / credential stuffing + lateral movement via Mimikatz & PsExec.
  3. EternalBlue / DoublePulsar (MS17-010) for lateral propagation—specifically an embedded 32-bit service DLL carrying the AES-NI encryptor.
  4. ESXi Linux variant exploits CVE-2019-5544 (VMware SOAP race condition) to shutdown VMs first, then encrypt .vmdk images.
  5. Watering-hole infection of compromised Ukrainian accounting websites leading to malicious MSI installer.

────────────────────────────────────────

Remediation & Recovery Strategies

────────────────────────────────────────

1. Prevention

  • Patch immediately: MS17-010 (Windows), TLS & Samba share fixes (Linux), ESXi patches ESXi670-201912001, ESXi650-201912001.
  • Disable SMBv1 across the domain (GPO + PowerShell Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol).
  • RDP lock-down: Network-level authentication (NLA), 2-factor, strong passwords, and rate-limiters (e.g., IPBan, RdpGuard).
  • E-mail gateway filters: Block .doc,.rtf,.js macros and .hta,.wsf,.lnk attachments; set macro execution to signed-Only.
  • Least-privilege: Remove domain-join for admin workstations; disable plaintext credential storage (Protect-ADAccounts.ps1).
  • Offline & immutable backups (3-2-1 rule) before any infection; verify daily test-restores.

2. Removal (Step-by-Step)

  1. Isolate the endpoint from LAN + Wi-Fi (pull cable or block via NAC).
  2. Identify run-key persistence:
    – HKCU\Software\Microsoft\Windows\CurrentVersion\Run or HKLM\...\Run containing svchost.exe–random.
    – Remove scheduled task MicrosoftNetwork pointing to %APPDATA%\{GUID}.exe.
  3. Stop Server, uRPC, double-spawned tasksche.exe services via sc stop & recovery-mode boot.
  4. Delete binaries:
    – %APPDATA%\{random}\svchost.exe (actual ransomware);
    – %TEMP%\ntuser.dat.
  5. Run full cloud-reputation or offline AV scan (ESET, Bitdefender, Windows Defender with latest Trojan.Win32.AESNI.. signatures).
  6. Re-image if environment is high-value; otherwise proceed with decryption tools if available.

3. File Decryption & Recovery

  • Recovery feasibility: YES – free decryption tools exist for versions used before July 2018 (static RSA-2048 seed key aes_ni_0xa3…).
    ➜ Tool: aesnidecrypter.exe v2.2.2 (Emsisoft + CERT.pl joint release).
    – Runs fully offline; requires victim ID left in !!!README!!!.txt.
    – ESXi binaries (hatched 2021) use embedded key; no public decryptor at time of writing—rely on backups only.
  • Essential tools/patches to have on hand:
    – Emsisoft decryptor – https://decryptor.emsisoft.com/aes-ni
    – ESXi: VMware vSphere Hypervisor 6.7 U3c cumulative patch
    – Windows March-2023 cumulative patch (contains SMBGhost, BlueKeep mitigations)

4. Other Critical Information

  • Differentiating characteristics:
    – Utilises hardware AES-NI x86 instruction set for performance; hence name.
    – Adds files-to-exclude whitelist (\\Windows\\System32\\…) to avoid BSOD; powers-down services via net stop vssadmin to cripple shadow-copy recovery.
    – Ransom note (!!!README!!!.txt) includes unique TOR “Session ID”, demands $210–$500 USD; affiliates often ask for Monero.
  • Broader impact:
    – Major waves hit Ukrainian gov’t & energy sector in 2018, creating a surge in Cyber-aid Ukraine on-the-ground remediation efforts.
    – Spawned copy-cat encryptors (e.g., FilesLocker 2.1) that reuse AES-NI code fragments.
    – Demonstrated that cryptographically-speedy ransomware can still be defeated if operators were sloppy with key storage, highlighting the importance of timely key seizures.

────────────────────────────────────────
Action Summary

  1. Patch, harden, and segregate NOW if you haven’t since 2017.
  2. First check for the untouched decryptor when you see “.aes_ni”; you might walk away without paying.
  3. Keep disks/volumes offline-ready—because the 2021 ESXi strain has no free fix.

Combat this threat. Stay resilient.