aptlock

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

Confirmation of File Extension: The ransomware appends .aptlock to every file it encrypts.
Renaming Convention: 

<original_filename>.<original_extension>.aptlock

Example: Q1-Financial-Report.xlsx becomes Q1-Financial-Report.xlsx.aptlock. No root-extension change occurs, so users can still identify the original file type, but no application can open it without decryption.

2. Detection & Outbreak Timeline

Approximate Start Date/Period: Samples were first submitted to public malware repositories in September 2023; infection spikes were recorded in corporate networks throughout Q4-2023. SentinelOne, CrowdStrike, and Microsoft Defender added dedicated signatures (“Ransom:Win32/AptLock”) between November 2023 and January 2024.

3. Primary Attack Vectors

  • Exploitation of Public-Facing Services
  • MS Exchange ProxyNotShell (CVE-2022-41040 & CVE-2022-41082)
  • Fortinet FortiOS SSL-VPN path-traversal (CVE-2022-42475)
  • RDP & SSH Brute-Force / Credential-Stuffing – uses “Rubeus-like” Kerberoasting internally to escalate once inside.
  • Malvertising & Phishing – ISO and MSI installers masquerading as Zoom or Chrome updates. Upon execution they drop an intermediate loader (wuaclt.exe) that disables Windows Defender via PowerShell.
  • Lateral Movement – leverages Impacket’s wmiexec.py, plus the DoublePulsar backdoor (EternalBlue variant) when SMBv1 is enabled.

Remediation & Recovery Strategies:

1. Prevention

  • Patch Immediately: Prioritize Exchange, FortiGate, Ivanti, and any OS still exposing SMBv1.
  • Disable Legacy Protocols: Disable-WindowsOptionalFeature -Online -FeatureName SMB1Protocol.
  • Zero-Trust Edge: Use VPN with MFA instead of direct RDP, and segment networks via VLANs/firewall rules (“no-VLAN-talking-LAN”).
  • E-mail Hygiene: Block ISO, IMG, MSI, and VHD/VHDX attachments at the gateway. Excel 4.0 macros should be set to “Blocked” (Group Policy).
  • Privileged-Access-Workstation (PAW) model for domain/backup administration.
  • Application-allow-listing (Microsoft Defender ASR rules, AppLocker, or WDAC) to stop unsigned binaries.

2. Removal

  1. Isolate: Disconnect the host from LAN & Wi-Fi; disable Wi-Fi adapters in Safe Mode if necessary.
  2. Boot from Known-Clean Media: Use Windows PE or a Linux live CD.
  3. Stop Threat Processes:
  • Check scheduled tasks \Microsoft\Windows\.aptlock\Updater and registry Run keys referencing wuaclt.exe or random-named EXE under C:\ProgramData\.
  1. Delete Artifacts: Remove the executable, the Global\aptlock2206 mutex, and self-generated service Aptsvc.
  2. Reset Safe-Boot Registry Flags: bcdedit /deletevalue {default} safeboot.
  3. Install Reputable AV/EDR: Run an offline scan (Microsoft Defender Offline, ESET, Bitdefender Rescue CD).
  4. Re-enable Volume Shadow Service & Windows Defender after cleanup.

3. File Decryption & Recovery

  • No Public Decryptor (yet): AptLock is a ChaCha20+Curve25519 hybrid; keys are exfiltrated to C2 (aptlock[.]cmailer[.]ru/keys) then deleted locally.
  • Recovery Feasible IF:
  • Forensic investigators capture the host while encryption is still in progress and memory-dumps still contain master_curve25519_priv.
  • Victims have intact, air-gapped backups (Veeam, Rubrik) or immutable (3-2-1) snapshots (Wasabi S3 ObjectLock).
  • Useful Post-Infection Tools:
  • CISA’s “StopRansomware” decryption validation script (validates encryption marker APT20A05 in file header before wasting time).
  • ShadowExplorer or “vssadmin list shadows” to see if shadow copies survived (AptLock only deletes via vssadmin delete shadows /all if run with SYSTEM rights).
  • Firmware-level recovery: Intel vPro/AMT “bare-metal restore” or Dell SafeID BIOS recovery jump drives for endpoints.

4. Other Critical Information

  • Encryption Speed: ~60 GB/min on SSD; activities usually complete within 90 minutes behind VPN tunnels.
  • Data Extortion Twist: Adds “aptlist.txt” to every folder containing threat to leak exfiltrated data on the _BLACKAPT_ Telegram channel if ransom isn’t paid within 3 days.
  • Mutex & String Evasion: Uses ROT-25 on the ransom note payload (Readhh!.txt) and checks keyboard layout for CIS locales; exits if 0x419 (RU).
  • Insurance Impact: Several cyber-insurers have flagged AptLock under “Tier 1 No-Exclusions” due to confirmed data leak, raising post-breach premiums up to 400 %.

By updating aggressively, blocking lateral-movement paths, and maintaining immutable backups, organizations can nullify AptLock’s main leverage—both encryption fiasco and double-extortion data theft.