Task Manager showing higher CPU than sum of all processes- malware?

ryukamii said:

My computer’s task manager has always shown a higher cpu than the sum of all the processes being used. It’s been like this for a long time and I thought it was normal, but after norton blocked a coinminer from a website that used adobe flash I began to think that I have hidden malware installed on my computer. After norton detected the attack I did a full system scan using Malwarebytes Free and nothing came up, which is really making me worried because I have no way to check if I have malware installed or not. Are there any other methods of checking to see if I have something malicious? I’m scared to restart my computer because I know malware can screw things up upon restarts.

First, a coinminer is a nuisance, not a real malware or virus. They use part of the CPU to do their thing. Although a pain, it is not an indication of your machine being infested with malware. Not making light of your concern, but I don't want you to over react either. Norton blocking it is good, it's doing it's job. As far as you seeing taskmanager reporting difference in CPU calcs, yes, that's been around for a very long time. By the time some of the calcs are done for one reporting section, they have changed in another..... so it's pretty impossible to get all areas in taskmanager to calc and report the exact same numbers simultaneously. Unless you see a really big disparity, don't worry about it.

ryukamii said:

My computer’s task manager has always shown a higher cpu than the sum of all the processes being used.

For starters, the default task manager is a joke, try something decent, like:

ProcessExplorer or Processhacker or Anvir.

ryukamii said:

Are there any other methods of checking to see if I have something malicious?

Never rely just on one scanner, try more: emsisoft - kaspersky - eset

rkill it a little more specialized, but it can also remove something legitimate.

Autoruns will show almost anything set to run at startup, even fileless malware.