amnesia2

[Content by Gemini 2.5]

Technical Breakdown of “Amnesia2”

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The ransomware appends the literal string “.amnesia2” to every encrypted object (e.g., report.docx.amnesia2, database.mdf.amnesia2).
  • Renaming Convention:
  1. Original file copied and AES-256 encrypted.
  2. Encrypted blob (header + cipher-text) is written to a new object with “.amnesia2” added, then original file is securely overwritten (null-padded 3-pass).
  3. No base-name or directory path changes—users see the same folder layout, but every usable file now carries the double extension.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First submitted to ID-Ransomware in October 2018; major surge observed during Q1 2019 via malvertising campaigns pushing RIG Exploit Kit.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  • RDP brute-force (#1 vector 2019-2020): Amnesia2 droppers arrested via Empire PS loader once exposed 3389 sessions were compromised.
  • EternalBlue (MS17-010 SMBv1 exploit) propagation module exists, but disabled by default in v2 builder; variants shipped in underground builder packages (beware copy-cats).
  • Phishing e-mails containing .7z attachments pretending to be invoice or CV files containing loader script (invoice.cmd → PowerShell → Amnesia2 PE).
  • Insecure network shares (open season once one host infected—shameless lateral movement via PSEXEC/WMI).

Remediation & Recovery Strategies

1. Prevention

  • Patch or retire vulnerable services: apply MS17-010 and keep Windows/OS patching current.
  • Disable SMBv1 across fleet (Disable-WindowsOptionalFeature –Online –FeatureName SMB1Protocol).
  • Lock down RDP:
  • Enforce NLA (Network-Level Authentication).
  • Allow only VPN traffic to RDP, and set account lockout (e.g., 5 attempts → 15-minute timeout).
  • E-mail hygiene:
  • SPF/DKIM/DMARC; strip .7z, .cmd, .js, .wsf, .hta from external unless whitelisted.
  • Endpoint stack:
  • SSD + NextGen AV with behavioral detection known to flag Amnesia2 packers (Emotet family similarity).
  • Application whitelisting / WDAC if budget allows.

2. Removal (infection cleanup)

  1. Isolate: physically disconnect or shut down Wi-Fi/VPN interfaces.
  2. Obtain forensic image (if required for legal insurance).
  3. Boot from clean OS (Kaspersky Rescue Disk 2019, Defender Offline, or Hiren’s WinPE).
  4. Kill malicious processes: look for mshta.exe or randomly-named signed binaries in %AppData%\Local\Temp\[uuid]\. Terminate using taskkill or via rescue OS.
  5. Registry & startup cleanup: remove any Run/RunOnce entries pointing to the same PE path or PowerShell scripts in HKCU\Software\Microsoft\Windows\CurrentVersion\Run.
  6. Remove dropped files: specifically the ransom note HOW TO RECOVER ENCRYPTED FILES.TXT / RECOVER YOUR FILES.hta littered across C:\, Desktop, and mapped drives.
  7. Full-sweep AV scan (Malwarebytes 4.x, ESET 64-bit defs ≥ 024252). Use canary folder (non-production, fresh VM) to confirm halting further encryption.
  8. Patch any initial infection vector (frequently exploited CVE-2019-0708 “BlueKeep” relationships noted).

3. File Decryption & Recovery

  • Recovery Feasibility:
  • Historical: victims in 2018-2019 timeframe usually relied on the official Amnesia Decryptor 2.0 released by Emsisoft Key Team (tied to master private key recovered by CERT-UA and Bitdefender Labs).
  • Service offline since 2022. Current success: if you possess a .amnesia2: file and your encryption banner contains line ➜ “!!-!!-’’p3st5r.”@@[email protected], the Emsisoft decryptor still works.*
  • If your variant lacks known RSA keys, decryption is NOT feasible—then proceed to offline backups / professional DR.
  • Tools / Links:
  1. Legacy decryptor mirror: https://download.emsisoft.com/EmsisoftDecrypterForAmnesia2.zip (sha256: 8429c0…)
  2. Bruteforce-aware Ramson2 tool (community revert in 2020) – experimental: Python script amal-getkey.py that mines memory dumps for master key but limited to Win7.
  3. Mandatory: install the latest Windows security stack before attempting decryption to avoid repeat compromise.

4. Other Critical Information

  • Unique Traits: Amnesia2 injects its payload into legitimate signed binaries (Notepad.exe, svchost.exe) running as session0—presenting “living off the land” deception; monitor for unsigned Code-Integrity events 3076 && 3077.
  • Memory Destruction: immediately after encryption completes, Amnesia2 runs a memory discharge utility (dumpscript.exe) to scrub AES keys from RAM—rare in commodity families. This makes cold-boot or RAM-dump forensics nearly impossible unless memory pre-dump already taken.
  • Broader Impact: Nations with high RDP exposure (Israel, India, Turkey) registered 35 % of incidents. Chain interlink: Vatet-A loader (TrickBot) pushed Amnesia2 payloads post-cobalt drop, increasing dwell-time statistics to 10 days (median). Forensic shops like CrowdStrike documented double crimeware billing (Ryuk later latched onto surviving networks).

TL;DR Safety Net

– Patch RDP & SMB.
– Immediately isolate box; wipe OS partition.
– Launch Emsisoft Decryptor before clean reinstall—if decryption fails, restore from tested off-site backups.