Now, I want to preface: I'd never seen an attack like this on a Mac before in my life, and finding this kind of full-Mac hijack is very rare. And worst of all, they'd seemingly added a bunch of nonsense files into this computer's Library folder, with random folder names like 'prestidigitation' and 'beeswax'. Upon further investigation, I found a couple of self-professed 'Mac security programs' that popped up, demanding money to 'clean your Mac from junk'. We got rid of the browser hijack pretty quickly - I suggest using Cella's excellent how-to if you ever run into a browser hijack yourself - but the slowdowns were more curious. It was clear to me that his browser had been hijacked.
My father-in-law's MacBook Pro had been running into curious slowdowns for a two-year-old laptop and he kept on seeing weird sites taking over his Safari and Firefox search bars. Serenity Caldwell writing for iMore in 2017:
The problem: Mac malware in the Library folder
There are things you can do without having to burn it all down. It happens to the best of us (not me, of course). If your Mac is running slow or you're seeing unusual advertisements within your web browser you might have accidentally installed malware at some point. Though it's not easy to hack into or break through a Mac's security, it is possible, especially if someone accidentally installs malware without realizing it.
