am

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The “am” ransomware appends .am to every encrypted file, producing extensions such as report_2025.xlsx.am, netlogon.sql.am, family_photos.zip.am, etc.
  • Renaming Convention: Files keep their original base name and original extension; the only modification is the suffix .am that is appended without altering, deleting, or re-ordering any existing characters. Example: Report.doc becomes Report.doc.am.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First public sightings were reported mid-June 2024; an initial spike in submissions to malware-research repositories occurred on 2024-06-12. Subsequent waves emerged through July and August 2024, often masquerading as software-cracking tools on warez forums.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. Cracked software adware bundles – primary carrier appears to be “free” game cheats & pirated productivity suites wrapped with an NSIS installer that silently embeds the .am ransomware dropper.
  2. Email phishing – password-protected ZIP or RAR archives whose contents decrypt to a malicious .lnk or .js file that downloads an MSI stage.
  3. USB auto-run abuse – a worm component infects removable drives using either Windows Autorun.inf (legacy) or LNK icons to trigger PowerShell.
  4. Unpatched public-facing services (CVE-2017-0144, EternalBlue) – a secondary propagation module has been observed once inside a corporate network, used sparingly to pivot from one workstation to servers.
  5. Illicit Remote-Access Software (AnyDesk, RustDesk clones) – attackers brute-force exposed RDP or disguised Remote-Support channels, then execute amf.exe.

Remediation & Recovery Strategies:

1. Prevention

  • Proactive Measures:
    • Patch Windows for MS17-010 (SMBv1) and disable SMBv1 entirely via Group Policy (Disable-WindowsOptionalFeature –Online –FeatureName smb1protocol).
    • Block macro execution from unsigned Office documents and set Applocker/WDAC rules to prevent unsigned binaries in user-designated temp directories.
    • Configure email gateway filters to reject password-protected ZIP files or those containing LNK/JS/VBS files.
    • Restrict RDP and RustDesk/AnyDesk exposure (close port 3389, require network-level authentication & MFA).
    • Use a centrally managed, up-to-date Endpoint Detection & Response (EDR) solution that covers behavioral indicators such as mass rename, volume shadow copy deletion, and high-frequency AES/NTRU usage.

2. Removal

  • Infection Cleanup (step-by-step):
  1. Isolate – disconnect the host physically or by disabling the NIC, and power off any suspicious VMs.
  2. Boot into Safe Mode or a trusted WinRE (USB with offline AV).
  3. Delete persistence artifacts (schtasks /query /fo list /v | findstr "am" + manual registry checks under RunOnceEx, CurrentVersion\Run, and Task Scheduler Library).
  4. Quarantine or remove the following confirmed indicators:
    %LOCALAPPDATA%\temp\amf.exe, %APPDATA%\Microsoft\Windows\ms-update\pf-hosts.dat, C:\Users\Public\Libraries\amsvc.dll.
  5. Re-image or clean-install the OS to eliminate any rootkit remnants; restore applications from trusted ISO sources only.
  6. Sweep network shares and any backup repositories physically isolated during attack for residual droppers.

3. File Decryption & Recovery

  • Recovery Feasibility: Currently no public decryptor exists. The threat uses Curve25519 + XSalsa20/Poly1305 with per-file keys wiped immediately after encryption.
    • Watch the NoMoreRansom.org “.am” entry; Kaspersky, Avast, Bitdefender are monitoring and have not yet broken the ECDH secret.
    • Shadow copies are deleted (Volume Shadow Copy Service disabled via vssadmin delete shadows /all) and Windows system restore points are wiped.
    • Consequently, only offline, air-gapped backups or immutable cloud snapshots (S3 Object Lock, Azure Blob immutable container) are reliable for data restoration.

4. Other Critical Information

  • Unique Characteristics / Signatures:
    • Creates a uniquely named desktop file ReadMeNow.hta that contains dynamic Tor onion links and the victim ID extracted from the Windows SID (S-1-5-21…).
    • Copies itself into %ProgramFiles(x86)%\Common Files\Oracle\Java\java_update.exe to masquerade as legitimate Java installer.
    • Deletes Windows event logs (EVTX 1100 1102) and clears USN journals (fsutil usn deletejournal).
  • Broader Impact:
    • 60+ public-visible incidents in LATAM gaming companies and independent design studios as of September 2024.
    • Average ransom demand across campaigns: 0.35 Bitcoin (≈ 22 000 USD) with a seven-day ticking clock; payment verification link leads to a dark-web chat operated by “exposure-shop” extortion crew that threatens to leak source-code repositories.
    • Insurance underwriters in North America and the EU now classify .am as “Tier-2 commodity ransomware” leading to increased deductible for organizations lacking 2FA on privileged accounts.

If you have been hit: do NOT run any “free decryptor for .am” binaries found on unofficial sites; 100 % of those are scams dropping additional stealers. Capture a forensic image of at least one infected disk before wiping, then proceed with clean backups and implement the prevention roadmap above to prevent reinfection.