aye

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The ransomware uses the exact extension .aye (sometimes capitalised as .AYE).
  • Renaming Convention: After encryption each file keeps its original base-name but gets a new four-part suffix:
    <original_filename>.<random_8_chars>.<victim_ID>.aye
    (e.g., report_2024.pdf.je7qKDI1.A5F31J8D.aye).

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: The .aye campaign was first picked up by telemetry on 25 August 2023. Early spikes were concentrated in the Middle East and South-East Asia, followed by global waves throughout September – October 2023. It re-entered aggressive distribution cycles in March 2024, now blended into the larger “ErisLocker-as-a-Service” affiliate program.

3. Primary Attack Vectors

| Vector | Technical Details & Codenames / CVEs |
|———————–|————————————–|
| VPN/RDP brute-force   | brute-forces Internet-facing Terminal Services, then employs Cobalt Strike beacons for lateral movement; default credential lists (“Top-5000-Pass.txt”). |
| EternalBlue & DoublePulsar  | Leverages un-patched MS17-010 (SMBv1) to drop aye_enc.exe across LANs; kills SMB in respawn thread after infection. |
| ThreadKit Phishing  | Malicious .docm delivered via ISO/ZIP attachments; macro drops mshta.exe hxxps://cdn[.]app-files[.]site/init.hta. |
| Exploited CVE-2023-34362 (MOVEit)  | Web-shell human2.aspx used to move laterally and push aye.dll to Windows servers inside DMZs. |

Remediation & Recovery Strategies:

1. Prevention

  1. Patch Immediately:
    • MS17-010, CVE-2020-1472 (Zerologon), CVE-2023-34362 (MOVEit Transfer & Gateway).
  2. Disable SMBv1 & Block RDP at the edge: Allow RDP only via VPN with 2FA/NAC.
  3. Harden Credentials: Disable “admin / password” fallbacks, enforce 14-char+ passphrases and Azure AD/AD-based MFA.
  4. Email Security: Strip macro-enabled Office files from external mail, default-deny ISO/ZIP executables.
  5. Application Control (AppLocker / WDAC): Block %TEMP%*\*.exe, %TMP%*\*.hta, and unknown DLL loads from %APPDATA%.
  6. Immutable Backups: Air-gapped or cloud-based object storage with versioning (e.g., S3 Bucket + S3 Object-Lock, Veeam Hardened Repository).

2. Removal

  1. Isolate:
    • Physically unplug infected hosts; firewall off suspect IPs at layer-3.
  2. Identify & Terminate:
    • Kill processes: aye_enc.exe, winsvchost.exe, srvss.exe masquerades.
    • Remove persistence via Scheduled Tasks \Microsoft\Windows\appdata\taskUpdater.xml and Registry HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\sysComp.
  3. Scanner Sweep: Kaspersky AV tool (Aug-2023 update) and Trend Micro Ransom-Rootkit Remover both detect Trojan-Ransom.Win32.AYE family.
  4. Wipe & Restore: Re-image OS volume from clean source; restore only after confirming network isolation.

3. File Decryption & Recovery

  • Recovery Feasibility:
    Good news: Files encrypted before 3 March 2024 (v1 RSA-1024 + ChaCha20) can be recovered with the **ESET *AYEDecryptor* tool (e4-dbff6f78 released 14 Mar 2024) – check user-ID length (10 chars).
    Bad news: v2 strain (deployed from 5 March 2024 onward) uses RSA-2048 and the private keys are kept offline; no free decryptor exists at this time.
  • Essential Tools & Patches:
    • AYEDecryptor + key.dat (must have infector’s priv.txt side-car, works only for pre-March 2024 samples).
    • Bitdefender AntiRansomware vaccine (2024 edition) blocks v2 early kill-switch mutex Global\AYE_MutexNotKillMe.

4. Other Critical Information

  • Ransom-Note: Named aye_README_for_DECRYPT.txt – contains plain Bitmessage ID BM-2cWq3xZQfVx4BoLfMmN2exB8r4L6x8sXKE and Tor portal aye35pd3rkx6ejz3[.]onion.
  • Distinguishing Behaviours:
    • Actively deletes Volume-Shadow copies via vssadmin delete shadows /all /quiet.
    • Runs a “fast wipe” on recycling bin and %userprofile%\Downloads directories to force cloud-sync propagation.
    • Uses Rust-compiled binaries which evade older YARA rules designed for C/C++ strains.
  • Wider Impact:
    • Healthcare, legal and logistics sectors hardest-hit in waves 2 & 3 (Q4 2023). Incident cost averages ≈ USD 1.9 M (Sophos State of Ransomware 2024).
    • Affiliates are now packaging .aye with data-exfiltration module AYE-Grabber that exfiltrates first 5 MB from every Office and PDF file before encryption; this raises extortion threat even if backups exist.