I was told years ago to never run real time virus protection software on Windows Servers. They would slow down the whole thing, especially when lots of file I/O is done. Like is the case when using Access databases in classic ASP web applications. But WordPress also seems to generate a lot of disk i/o, more than what I had expected.

I noticed that on my AWS server, by default, real time virus protection (known as Defender by Windows users) is switched on. So I took the challenge and checked out the difference in loading speed of my hosted websites with and without Defender switched on. The difference is ... massive.

With Defender switched off, websites load up to 70% faster. Good to know I think... I bet there are better virus scanners than Defender for Windows... but they all cost a fortune. Not sure they're worth it... I better stick to a good backup plan in case a virus hits.