Real-time Protection vs On-Demand Scanning

2 min read Infrastructure & DevOps Security

Real-time Protection vs On-Demand Scanning

Balancing real-time protection with system performance requires understanding different scanning modes and their implications. Real-time protection intercepts file operations, scanning content before access, while on-demand scanning checks files at scheduled intervals or manual initiation. Each approach offers distinct advantages for different use cases.

Real-time protection provides immediate threat detection but impacts system performance, particularly on file-intensive operations. Configure Windows Defender real-time protection with performance optimizations:

# Exclude specific paths from real-time scanning
Add-MpPreference -ExclusionPath "C:\DatabaseFiles", "D:\TempWorkFiles"
Add-MpPreference -ExclusionProcess "sqlservr.exe", "oracle.exe"
Add-MpPreference -ExclusionExtension ".log", ".tmp"

# Configure CPU usage limits
Set-MpPreference -ScanAvgCPULoadFactor 50

Linux real-time scanning configuration varies by solution. For ClamAV with fanotify support:

# Enable fanotify for real-time scanning
echo "ScanOnAccess true" >> /etc/clamav/clamd.conf
echo "OnAccessMountPath /" >> /etc/clamav/clamd.conf
echo "OnAccessExcludePath /proc" >> /etc/clamav/clamd.conf
echo "OnAccessExcludePath /sys" >> /etc/clamav/clamd.conf
echo "OnAccessPrevention false" >> /etc/clamav/clamd.conf  # Detect only mode

On-demand scanning suits specific scenarios like pre-deployment checks or scheduled maintenance windows. Implement scheduled scans during low-activity periods:

# Linux scheduled scan with ClamAV
cat > /etc/cron.d/clamav-scan << EOF
0 2 * * 0 root /usr/bin/clamscan -r / --exclude-dir=/proc --exclude-dir=/sys --infected --log=/var/log/clamav/weekly-scan.log
EOF

# Windows scheduled scan
$action = New-ScheduledTaskAction -Execute "PowerShell.exe" -Argument "-Command Start-MpScan -ScanType FullScan"
$trigger = New-ScheduledTaskTrigger -Weekly -DaysOfWeek Sunday -At 2am
Register-ScheduledTask -TaskName "WeeklyAVScan" -Action $action -Trigger $trigger -RunLevel Highest

Performance optimization strategies minimize scanning impact while maintaining security. Implement intelligent scanning that checks files only on first access or after modifications. Use hash-based caching to avoid rescanning unchanged files. Configure multi-threaded scanning for better performance on multi-core systems.