Malwarebytes free slows internet dramatically

Just something to note.

Have used Malwarebytes free, on and off, for a few years, usually just to run a test to see if it can detect things Avast misses.

Last week I updated it and run a scan - nothing found, but forgot to disable it. Over the next few days the time taken to load pages increased dramatically. For example the ThinkBroadband speed tester was taking over 3 minutes to load to the point the test started.

Disabled the Malwarebytes program and service and it returned to almost instant loading.

Should maybe be retitled to "Security software scans slow any amount of system activities while running". Most do on some level or another, if not a real-time scan. Manual scans are more resource hungry, so maybe consider changing task priority of MWB scan process to alleviate the issue. Or learn to walk away from PC when running a scan.

MS Security Essentials does little CPU in real time, but CPU jumps to 15-25% when asked to do a quick scan (A8-7600 4 core CPU). My bigger system wouldn't notice it. Maybe your hardware spec is low-ish?

Absolutely. I recommend using this program a handful of times a year and uninstalling after every use. If its sat there going through every webpage and everything coming in and out your network it will slow down you PC.

I have the paid for version and it started totally blocking network access. I had to fully uninstall with their tool and then reinstall to clear. It may help with your free version if you use the Malwarebytes removal tool to fully remove and then try it again.

I leave mine installed but disable all services and scheduled tasks associated with it. Enable the service when I want to run it. As you say, a handful of times per year.