aes-ni

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .aes_ni
  • Renaming Convention:
    \<originalname\>.\<originalextension\>.aes_ni
    Example – a file called Quarterly_Report_Q3.xlsx becomes Quarterly_Report_Q3.xlsx.aes_ni.
    Note: Early variants used .aes-ni (with a dash), but later campaigns standardized on the underscore form .aes_ni.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period:
    First publicly observed in late December 2016; a larger wave hit worldwide in April 2017 after researchers leaked its SMB exploit capability.

3. Primary Attack Vectors

| Mechanism | Explanation & Notable Details |
|—|—|
| Remote Desktop Protocol (RDP) | Most common in 2023+ campaigns; attackers scan the Internet for exposed RDP (port 3389), then brute-force or replay stolen credentials to deploy the dropper. |
| EternalBlue / DoublePulsar | Older waves automatically spread within a LAN using the leaked NSA exploits against unpatched Windows (SMBv1, TCP 445). |
| Phishing & Malicious Attachments | ZIP, RAR, or ISO containing .js, .exe, or macro documents masquerading as invoices or COVID forms. Payload often a PowerShell downloader that fetches the AES-Ni binary from a remote C2. |
| Supply-chain Misconfigurations | Detected in MSP backup software using default credentials or vulnerable update components; attackers push the ransomware to multiple customer hosts simultaneously. |

Remediation & Recovery Strategies:

1. Prevention

  • Block RDP from the Internet via firewall; force VPN + MFA for any necessary remote access.
  • Patch early, patch often – MS17-010 (EternalBlue) and every subsequent critical OS/app patch.
  • Disable SMBv1 globally through Registry or Group Policy (sc.exe config lanmanworkstation depend= bowser/mrxsmb20/nsi).
  • Credential hygiene – enforce complex MFA, unique local admin passwords (LAPS), and monitor for new privileged logons.
  • Robust email filtering – strip macro-laden documents, ISO attachments, and .js files; enable SPF + DMARC DKIM checks.
  • Least-privilege & segmentation – isolate critical file shares; block lateral-movement ports (TCP 445, 135, 139) between VLANs.

2. Removal

  1. Disconnect infected host(s) from the network immediately (Wi-Fi, Ethernet, VPN).
  2. Stop malicious processes – open Task Manager → kill any *.exe files signed by unknown publishers or running from %TEMP%, C:\ProgramData, or %USERPROFILE%.
  3. Boot into Safe Mode (or Windows Recovery) to prevent the core service (AesNiService or randomly named Rasman clone) from relaunching.
  4. Delete persistence artefacts – Scheduled Tasks called “WindowsUpdate,” Registry run-keys under HKLM\..\Run, and start-up folders.
  5. Use reputable AV/EDR such as Microsoft Defender Offline, CrowdStrike Falcon, ESET, or Bitdefender with updated signatures (detection names: Ransom.AES-Ni, Win32/Filecoder.AESNI.A).
  6. Nuke-and-rebuild (gold image) – reinstall Windows from clean media after backing evidence (drive image) for forensics if needed.

3. File Decryption & Recovery

  • Recovery Feasibility:
    Partial YES (December 2016 – April 2017 victims). Subsequent campaigns updated key generation; NO reliable public decryptor exists after April-2017 builds.

  • Where to look:
    – Emsisoft Decryptor (covering v0, v1, v1.6 keys). Download only from emsisoft.com/decrypt-aes-ni.
    – Avast Decryptor. Useful for .aes-ni samples that leak the public key in ransom notes (!!! RESTORE FILES !!!.txt).
    – VirusTotal Intelligence – upload encrypted file + ransom note; AV engines sometimes tag older samples with a recoverable master key number.

  • Manual key extraction – in rare cases, the perpetrators reused the same RSA-1024 private key; aesni_keyfix.exe (open-source) can cross-reference known leaked keys.

4. Other Critical Information

  • Ransom Note Filenames vary: !!! RESTORE FILES !!!.txt, !!! READ THIS – IMPORTANT !!!.txt, DECRYPT-instructions.txt pinned to every folder and desktop.
  • BTC wallet reuse trend – Analysts track around 45 static wallets (1A0FxA6q4s9pB3…). Blockchain taint analysis has allowed seizure in some nation-state operations.
  • Immunization trick – AES-Ni writes mutex Global\XBF4KRKJ8XKVN to block multiple executions. Creating an empty file system object with the same name prevents re-infection on the same machine (used by some SOCs during outbreak cleanup).
  • Global impact highlights – Russian universities, Ukrainian ministries, and U.S. hospital networks Cambrige-HealtH & CHS victims in 2017 caused FDA advisory on medical devices.

Resilience against AES-Ni boils down to tight endpoint hardening, rigorous backup discipline (offline + immutable), and swift TTP blocking at firewall and email layers.