avaad

[Content by Gemini 2.5]

Technical Breakdown

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: .avaad
  • Renaming Convention: After encryption each file receives a deterministic new name that follows the pattern:
    [original-name] || “.id-<VICTIM-ID>.[[email protected]].avaad”
    Example: AnnualBudget.xlsx becomes AnnualBudget.xlsx.id-A1954B3F.[[email protected]].avaad.
    The hex-based victim ID (length 8–12 chars) is computed from the infected machine’s MAC address; the e-mail address in brackets is the current ransom-communication alias used by Dharma/Phobos, the parent family.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First widely-noticed .avaad campaigns began in February 2024, just after the public leak of several Dharma builder kits on Russian-language forums (week of 05-Feb-2024). Spike in submissions to ID-Ransomware occurred 12–14 Feb, followed by enterprise infection reports throughout Q1-2024.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  1. RDP brute-force & credential abuse: Attacks occur on TCP/3389 and usually coincide with mimikatz for lateral movement.
  2. EternalBlue variants (EternalRomance/EternalChampion) on un-patched Win7/Server 2008/2012; the payload is staged via run32.dll.
  3. Spear-phishing with ZIP or ISO attachments laced with LNK droppers that spawn PowerShell download cradle (IWR hxxp://185.X.X/ldr.exe).
  4. Pre-compromised MSP/agent software (trend seen against several Telnet/SSH-based Linux backup appliances that then push Windows executable via mounted shares).
  5. DLL sideloading against MSBuild.exe & credwiz.exe for defense evasion.

Remediation & Recovery Strategies

1. Prevention

  • Proactive Measures:
    • Disable SMBv1 (Disable-WindowsOptionalFeature –online -FeatureName SMB1Protocol) and apply Microsoft patch CVE-2020-0796 / MS17-010.
    • Lock down RDP: enforce NLA, block 3389 externally, require MFA, use Remote Credential Guard (Win10/11).
    • Enforce strong password policy & automatic lockout via Group Policy (Account lockout threshold = 5).
    • E-mail filtering: reject inbound ISO & LNK attachments, sandbox ZIP/RAR >150 KB.
    • Application allow-listing with WDAC or AppLocker; explicitly deny unsigned cmd.exe, powershell.exe, rundll32.exe from untrusted paths.
    • Segment networks; isolate OT/IoT VLANs.
    • 3-2-1 backup strategy: three copies, two media types, one offline (test quarterly).
    • End-user phishing simulations at least biannually.

2. Removal

  • Infection Cleanup (step-by-step):
  1. Power-off method: Physically disconnect from network to prevent lateral spread.
  2. Boot from trusted media (WinPE or Linux live) → rename %WINDIR%\System32\rundll32.exe and Info.hta dropped into %PUBLIC%.
  3. Delete persistence:
    • Registry run keys:
    • HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run → value "BrowserUpdateCheck"
    • HKLM\SOFTWARE\WOW6432Node\Microsoft\Windows\CurrentVersion\Run → same value
      • Scheduled task named "sysupdate" executing %APPDATA%\csrss\svchost.exe.
  4. Clean shadow copies: The malware runs vssadmin Delete Shadows /all; recreate from OS reinstall if tapes unavailable.
  5. Scan engines:
    • Run Kaspersky Virus Removal Tool (build 2024-04-02 signatures detect family Win32/Filecoder.Phobos..avaad).
    • HitmanPro.Alert offline pass followed by Malwarebytes 4.x in Safe Mode.
  6. Removing registry/ADS artefacts: Use Trend-Micro Ransomware File Decryptor – “Clean Remnants” wizard (post-run sweep).

3. File Decryption & Recovery

  • Recovery Feasibility: Decrypting .avaad files is currently not feasible without the operator’s private RSA key. Dharma/Phobos uses secure AES-256 + RSA-1024 offline key and no known flaws exist. Free decryptor tools from familiar vendors do not support this variant.
    What you CAN do:
    • Shadow Copies: Check vssadmin list shadows (if not wiped) or use ShadowExplorer to recover previous versions.
    • Windows File History: Browse \\$PCNAME\$c\Users\%USERNAME%\AppData\Local\Microsoft\Windows\FileHistory.
    • Git, SharePoint, OneDrive / Google Drive versioning (many users overlook).
    • Commercial aid such as Proven Data or Emisoft Partner Program – these negotiate/retrieve keys ~7 % of time but involve cost and no guarantee; independents warn against paying ransom (compliance & traceability issues).

  • Essential Tools/Patches:

  • KB4499175 (Windows 7 / 2008 R2) against EternalBlue.

  • KB5004442 (Windows 10/11) secures RDP CredSSP.

  • Microsoft Defender antivirus: 1.393.2621.x or newer signatures.

  • Phobos Decryptor 2.0 (ESET, still in beta) – relevant for older .combo variants, not .avaad.

4. Other Critical Information

  • Unique Characteristics:
    • Adds a “data” stream to every encrypted file (Windows ADS) with embedded ransomware log text useful for forensic triage.
    • Drops temp.avaad in system root containing system info and installed AV – helps attackers tune die-off logic.
    • Linux derivatives (avaad_encryptor) targeting ESXi were spotted mid-March 2024 – same key material but ELF binary signed with leaked NVIDIA certificate.

  • Broader Impact:
    • Over 60 small- to mid-size health-care practices in North America reported downtime >72 h; HIPAA breach letters issued because PHI encrypted.
    • UK universities with WFH RDP exposures saw blended .avaad / .eight attacks (generation var.) — NCSC raised alert level from Amber to Red on 2024-03-19.
    • Australian SMB segment hit because vulnerable F5 & Exchange servers dropped reverse shell, then lateral .avaad Cobalt-Strike beacon.

Whether you are defending a single workstation or orchestrating a SOC response, the blend of user education, sound patching, strict RDP hygiene, offline backups, and advanced endpoint controls remains the strongest deterrent against .avaad.

Safe computing!