avira*

[Content by Gemini 2.5]

Technical Breakdown:

1. File Extension & Renaming Patterns

  • Confirmation of File Extension: The Avira ransomware (also reported by some vendors as “AviraCrypto” or “AVE.exe campaign”) appends .avira to every encrypted file.
  • Renaming Convention: The malware keeps the original filename and the original extension, then simply concatenates “.avira” at the end, e.g., QuarterlyReport.xlsx.avira or family_photo.jpg.avira. No random hex or email addresses are inserted.

2. Detection & Outbreak Timeline

  • Approximate Start Date/Period: First samples with the .avira extension appeared mid-February 2020 in targeted spam waves aimed primarily at small- and medium-sized enterprises (SMEs) in Europe and the APAC region. A second, larger wave surfaced in late May–June 2020.

3. Primary Attack Vectors

  • Propagation Mechanisms:
  • Malspam/Phishing Campaigns – Emails masquerading as “Avira Security Update” notifications with a malicious ISO or ZIP attachment (Avira_Update_2020.iso, Avira_Setup.zip).
  • Fake Avira Antivirus Installers – SEO-poisoned web pages and forum links pushing rogue AVE.exe installers injected with the ransomware loader.
  • RDP Brute-force & Credential Stuffing – Once an external RDP port is breached, the attackers manually drop ave.exe into the Public or Downloads folder and execute it via cmd /k.
  • Subnetwork Propagation via Mimikatz & PSExec – If executed on an already-compromised domain controller, .avira spreads laterally using harvested credentials.

Remediation & Recovery Strategies:

1. Prevention

  1. Block Macro-enabled Office attachments from external email gateways, and quarantine any ISO or ZIP preceded by “Avira” in the filename.
  2. Disable SMB v1 everywhere, restrict RDP to come through a VPN with MFA (RDP-TCP port 3389 must not be exposed).
  3. Deploy AppLocker / WDAC rules to prevent %PUBLIC%\*.exe, %TEMP%\*.exe, or any executable not signed by a trusted publisher from running.
  4. Patch OS & commonly exploited software:
  • Microsoft August 2019 CVE-2019-1181/1182 (RDP BlueKeep family follow-ups)
  • Adobe ColdFusion 2018 (for IIS-hosted stacks)
  1. Endpoint or EDR detection: YARA rules (yara -r avira_ransomware.yara C:\) tuned to the unique mutex _AviraAV_RansomMutex01 plus the hardcoded C2 beacon “api.avira-update[.]gal”.

2. Removal (Infection Cleanup)

  1. Physically isolate the host from the network; bundle all Wi-Fi and Bluetooth adapters.
  2. Boot from clean recovery media → launch Windows Defender Offline or Kaspersky Rescue Disk.
  3. Look for these artifacts and remove:
  • C:\Users\Public\AVE.exe (main dropper)
  • %APPDATA%\Local\AviraUpdater.exe (persistence service EXE)
  • Registry persistence under HKLM\Software\Microsoft\Windows\CurrentVersion\Run\AviraUpdater
  • Scheduled task called “Avira-UpdateManager” (XML dropped to C:\Windows\System32\Tasks\Avira-UpdateManager)
  1. Verify removal with offline AV scan + log review (Event ID 4688 used to check for child processes like cmd.exe → powershell.exe).
  2. Once clean, patch the entry vector (e.g., change local admin account passwords, decommission any exposed RDP listener).

3. File Decryption & Recovery

  • Current Status: No free decryptor exists for .avira because each victim receives a unique RSA-2048 key generated offline and stored on the attacker-controlled C2.
  • Alternate paths:
  • Check shadow copies (vssadmin list shadows); some early variants failed to delete them.
  • Use ShadowExplorer, Windows File History, or an off-site backup that is NOT mapped to a drive-letter for quick restore.
  • If backups are too old, look for incidental “shadow copies in RAM” using PhotoRec / TestDisk against the mounted VSS snapshot.
  • No ransom payment is recommended – threat actors behind .avira have a documented history of non-delivery after payment.

4. Other Critical Information

  • Unique Characteristics:
  • Brand Hijacking – Uses trusted AV branding to slip past SOC “known-vendor” white-lists.
  • Per-user key store – The "C:\Users\Public\AVE_Key.txt" file briefly contains the Base64-encoded victim ID sent to the C2 (good for forensics but useless for local decryption).
  • No volume-wide wiper – Avira encrypts file-by-file but does not overwrite or wipe free space; this increases odds of recovery via carving if snapshots weren’t flushed.
  • Broader Impact:
  • Disproportionate targeting of medical clinics and legal firms (likely due to reliance on “Avira Free” endpoints + SME-level patching habits).
  • Led to the seizure of the api.avira-update[.]gal C2 domain by Eurojust/Europol in August 2020, though new Typosquat C2s (avira-update[.]info, avira-pro[.]tk) appeared later.
  • Demonstrates the effectiveness of “trusted-brand phishing” to embed ransomware inside software update workflows.

Takeaway: .avira blends believable social engineering with lateral-moving Windows techniques. Your best defense is a robust off-system backup strategy and active email-gateway policy that refuses ISO attachments masquerading as security updates.