A new research conducted by AV-Comparatives determined the security solutions with the biggest impact on system performance in Windows 10, and the results are surprising, to say the least.

The test was performed on a Lenovo G50 powered by an Intel Core i3 chip, 4GB RAM, and HDD, running Windows 10 Fall Creators Update and all applications installed with the default settings. AV-Comparatives ran a series of tasks like file copying, archiving and unarchiving, installing and remove apps, launching programs, downloading files, browsing websites, and PC Mark 10 benchmarks.

The most unexpected performance was recorded when testing Microsoft’s Windows Defender, which comes pre-installed in Windows 10.

Windows Defender performance

Windows Defender caused a substantial drop in performance during file copying and installing apps, with a smaller impact during the downloading of files. Microsoft’s security solution achieved 96.7 points in the PC Mark score, which isn’t as good as Avira’s 99.4-point score, but also not as bad as Quick Heal’s 95.2 points.

Windows Defender achieved a standard performance rating, while applications from Avast, AVG, Bitdefender, and Kaspersky got the best scores to secure an Advanced+ performance award.

The majority of antivirus solutions barely impacted performance when browsing websites or copying files, but the biggest slowdown was recorded when launching apps for the first time. Tencent, Trend Micro, Emsisoft, and VIPRE security products slow down systems on the first run of newly-installed apps.

“Although we list the results for the first opening and the subsequent openings, we consider the subsequent openings more important, as normally this operation is done several times by users, and optimization of the anti-virus products take place, minimizing their impact on the systems,” AV-Comparatives says.

Keep in mind that this research was conducted on a low-end device, so the performance impact might be substantially smaller in the case of computers with newer hardware.