Vidar Malware Removal Guide

Signs of Infection

Vidar infection manifests through several observable artifacts. On the file system, check for suspicious executables in user profile directories, particularly %APPDATA%, %LOCALAPPDATA%, and %TEMP%. Files may use random alphanumeric names (e.g., f7s83n.exe, setup.tmp) or attempt to masquerade as legitimate software. Look for recently created log files (e.g., logs.dat, system.txt) in these folders, as Vidar often stores stolen data locally before exfiltration.

Process behavior is a key indicator. Use a process monitoring tool to identify processes with mismatched parent/child relationships, high outbound network traffic, or attempts to access sensitive system resources like credential vaults and browser data directories. A common Vidar tactic is process hollowing or injection into a trusted system process (like explorer.exe or svchost.exe) to evade detection.

Network signs include connections to suspicious domains or IP addresses associated with Vidar’s command-and-control (C2) infrastructure. Traffic often uses HTTPS on non-standard ports to blend in. Look for beaconing activity - regular, periodic outbound connections - and data uploads to these endpoints, which may contain compressed or encrypted exfiltrated data.

Persistent registry entries are frequently created under paths like HKCU\Software\Microsoft\Windows\CurrentVersion\Run or HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run with values pointing to the malicious executable. Also check for suspicious scheduled tasks or services created to maintain persistence.

Immediate Containment Steps

Within the first 15 minutes of detection, your priority is to prevent further data theft and lateral movement.

1. Network Isolation: Immediately disconnect the infected host from the network. This can be done by disabling its network adapter via the operating system or, more effectively, by quarantining the device at the network switch or firewall level. Block all inbound and outbound traffic to and from the host’s IP and MAC address.
2. Process Termination: Using a trusted endpoint security tool or command-line utility, identify and terminate all processes associated with Vidar. Do not rely solely on the Task Manager. Focus on the suspicious processes identified earlier, but be cautious of potential process injection. Terminating the primary process may trigger persistence mechanisms to restart it.
3. Credential Rotation Priorities: Assume all credentials stored on or used by the infected host are compromised. Begin rotating passwords in this order:
   • Domain administrator and local administrator accounts.
   • Service accounts used on the host.
   • User accounts that were logged into the host.
   • Any credentials for critical infrastructure (e.g., VPN, email, financial systems) accessed from the host.
   • Change passwords from a known-clean system and enforce multi-factor authentication where possible.
4. Preserve Evidence: Before removal, consider taking a forensic disk image or memory dump if investigation is required. At a minimum, collect relevant files (suspicious executables, logs), process lists, and network connection data for later analysis.

Manual Removal Process

Proceed with manual removal only after containment. Use a trusted, offline security toolset or boot from a clean, write-protected USB drive.

1. Terminate Malicious Processes:

   • Boot into Safe Mode with Networking to prevent most persistence mechanisms from loading.
   • Use the command line with administrative privileges to list and stop processes. Identify the PID of the malicious process and run: taskkill /f /pid [PID].
   • Also, stop any suspicious scheduled tasks: schtasks /end /tn "[Task Name]".

2. Delete Persistence Mechanisms:

   • Registry: Open the registry editor with administrative rights. Navigate to and delete any suspicious entries in:
     • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
     • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
     • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce
   • Scheduled Tasks: Open the Task Scheduler. Review the task library and delete any recently created or suspicious tasks with random names or triggers set for user logon or system startup.
   • Startup Folder: Check and clean the user and common startup folders: %APPDATA%\Microsoft\Windows\Start Menu\Programs\Startup and C:\ProgramData\Microsoft\Windows\Start Menu\Programs\StartUp.

3. Remove Dropped Files:

   • Navigate to the file locations identified during detection. Common paths include %APPDATA%, %LOCALAPPDATA%, %TEMP%, and C:\Windows\Temp.
   • Delete the primary malicious executable(s) and any associated files like configuration files (config.bin), data logs (data.log), or DLLs.
   • Empty the Recycle Bin after deletion.

4. Clean Registry Entries (Additional):

   • Search the registry for any other references to the file paths or names of the deleted malicious files and remove those keys/values. Exercise extreme caution to avoid deleting legitimate system keys.
   • Check for changes to file extension associations or other hijacking techniques under keys like HKEY_CLASSES_ROOT.

Verifying Removal

After completing the removal steps, verify the system is clean.

1. System Scans: Perform a full system scan using an updated, offline antivirus scanner and a dedicated anti-malware tool. Use a second, different scanning engine for a layered check.
2. Log Analysis: Review system logs (Event Viewer) for the period following removal. Look for failed service start events (Event ID 7000), errors related to missing files, or new suspicious events. Monitor security logs for unexpected logon attempts or process creation.
3. Network Traffic Monitoring: Before fully re-integrating the host, reconnect it to a monitored, isolated network segment. Use a network monitoring tool or SIEM platform to watch for any residual beaconing or connection attempts to known Vidar C2 IPs/domains. Allow the host to run for 24-48 hours in this controlled environment if possible.
4. Artifact Check: Re-examine the file system paths and registry keys used by Vidar to confirm they have not been recreated. Verify that no new suspicious scheduled tasks have appeared.

Post-Removal Security Hardening

To prevent reinfection, implement these security improvements.

1. Configuration Changes:

   • Apply the principle of least privilege. Ensure standard user accounts cannot install software or write to system directories.
   • Harden endpoint configurations by disabling unnecessary macros, restricting PowerShell script execution through execution policies, and blocking Office applications from creating child processes.
   • Implement application allowlisting to prevent execution of unauthorized binaries from user writable locations like %APPDATA% and %TEMP%.

2. Monitoring Rules:

   • Configure your EDR solution or SIEM platform to alert on specific Vidar-related behaviors. Key rules include:
     • Process creation from %TEMP% or %APPDATA% spawning cmd.exe, powershell.exe, or making network connections.
     • Multiple file accesses to browser SQLite databases (History, Login Data, Cookies files) within a short timeframe.
     • Outbound HTTPS connections to IP addresses in low-reputation geolocations or newly registered domains.
     • Creation of registry run keys or scheduled tasks by non-admin users or from unusual parent processes.

3. Policy Updates:

   • Update email filtering policies to block attachments commonly used to deliver Vidar (e.g., .iso, .img, .rar archives) or to flag emails with password-protected archives.
   • Enhance user awareness training to focus on the social engineering lures used by Vidar distributors, such as fake software cracks, invoice scams, and phishing emails.
   • Review and enforce a policy of regular, mandatory credential rotation for administrative accounts, especially after a security incident.
   • Ensure robust, offline backups are maintained and tested, providing a clean restoration path in case of severe infection.

For the most current technical indicators, refer to the Current Vidar IOCs. To understand detection efficacy, review the Detection Rate. For more background on this threat, see the Vidar Overview.