We previously recommended Microsoft Defender for Endpoint full scans as a configuration best practice in this article, since that is the most secure option. While full scans offer the most comprehensive protection, they come with significant system resource consumption, which can impact performance. This blog article explores the benefits and drawbacks of full and quick scans and provides best practices for optimizing your Microsoft Defender for Endpoint configuration.
Full Scans vs. Quick Scans: Understanding the Difference
Advantages of Full Scans
A full scan thoroughly examines all files, connected network drives, archives, running processes, and registry entries for malware, ensuring that no hidden threats linger undetected. Key benefits include:
- Comprehensive Threat Detection – Scans all system areas, including compressed files and deeper layers that quick scans might overlook.
- Detection of Dormant Malware – Identifies inactive malware that may not be immediately executed.
- Thorough Risk Assessment – Useful after installing Microsoft Defender Antivirus for the first time to identify pre-existing threats.
Limitations of Quick Scans
Quick scans focus on system-critical areas where malware is most likely to reside, such as running processes, system folders, and the registry. While much faster and less resource-intensive, quick scans might not detect:
- Malware embedded in deep storage locations.
- Dormant threats that are not actively running.
- Malicious files stored within compressed archives or less-accessed directories.
| Feature | Quick Scan | Full Scan |
| Scope | Scans only the most infected areas (Memory, startup files, registry, system folders, etc.) | Scans all files, running processes and all drives (including network and removable media) |
| Duration | Fast (a few minutes) | Slow (Can take hours, depending on disk size, file count and network drives) |
| CPU / Memory Impact | Low to Medium | High |
| Real-time Behavior | Targets active malware, rootkits and recent file changes | Comprehensive check of all files, including dormant ones |
| Scan Frequency | Recommended for daily/weekly use | After first installation and when responding to an incident |
| Detection Scope | Focuses on recent and active threats | Detects everything in quick scan scope and also dormant threats, deeply embedded malware and rarely accessed files |
| Cloud Protection | Uses cloud intelligence for real-time detection | Less reliance on cloud scanning during the process |
Cloud Detection and Real-Time Protection: Enhancing Security Efficiency
In addition to scheduled scans, Microsoft Defender for Endpoint leverages cloud-based threat detection and real-time protection to mitigate risks more effectively:
- Cloud-based Protection – Enables Microsoft Defender to leverage threat intelligence and machine learning to detect new malware variants quickly.
- Real-time Protection – Continuously scans files and processes in real-time, blocking threats before they can execute.
- Behavioral Analysis – Detects anomalous behavior and potential threats based on activity patterns, even if the signature is not recognized.
With these features, full scans become less critical on a frequent basis, as modern threats are often identified before they can establish a foothold.
Best Practices for Configuring Scan Policies
To maintain a balance between security and system performance, consider these best practices when configuring Microsoft Defender for Endpoint:
- Perform an Initial Full Scan – After enabling or installing Microsoft Defender Antivirus, run a full scan to detect any pre-existing threats.
- Customize Scan Policies by Device Role – Assign different scan configurations based on system function like SQL Server Collection (Minimize scanning of database files for performance), IIS Server Collection, Restricted Workstation Collection (Higher security settings) due to sensitive operations and Standard Workstation Collection (Balanced security and efficiency).
- Avoid Using Domain Controllers as File Servers – This reduces antivirus scanning on file shares, minimizing performance overhead.
- Consider File Hash Computation Impact – Defender computes file hashes for every scanned executable file if not previously recorded. While beneficial for security, it can impact performance, especially during large file transfers.
- Monitor CPU Throttling – Full scans can be CPU-intensive. Microsoft Defender allows CPU throttling, but the default settings are optimized for performance. Adjusting CPU limits unnecessarily can degrade scanning efficiency.
Conclusion: Quick Scans and Cloud Protection Are Often Sufficient
Unless an organization has an elevated risk profile or specific security needs that warrant frequent full scans, quick scans combined with cloud-based detection and real-time protection provide sufficient security while optimizing performance. By tailoring scan configurations based on system roles and leveraging modern threat detection mechanisms, enterprises can maintain a robust security posture without excessive resource consumption.
By implementing these best practices, organizations can ensure they remain protected against modern cyber threats while maintaining system efficiency. Are you looking to optimize your endpoint security strategy? Contact us today to get tailored guidance on securing your organization with Microsoft Defender for Endpoint.
