The same principles to purchase price Vs quality & longevity apply to computers as does to lawn mowers.
You get no more than you pay for but a high priced does not necessarily mean a quality machine.
If you are running Microsloth softwear on a mac then you are just a vunerable to most malwear as a PC user.
If you want to avoid 99,9999999% of computer criminals run linux on your mac and no Microsloth applications.
Better still by going that method you can use open source sharewear which if you pay the paltry $1- to $ 50 bost developers ask you get never ending unlimited support and free upgrades.
Go into your history and delete it do the same thing with the cashe.
Open up your bookmarks / favourites and go through every one, one at a time every one that comes up wrong, delete it then manually navigate to the desired web page, make sure it is real & not a Ghosting or Spoof page then remake the book mark.
If you are running mac OS then set up a new administrators account then change your account to a std user.
From the administrators account, set your account prefferences to "simple finder".
That way nothing you do in normal use can alter any application and more important , no web site you may have accidentally can do anything to any application on your computer so t makes it really hard for a sit to install any type of malwear on your machine .
Never ever type in the administrators name & password into the computer when you are using your account.
If you get pop ups ( I have them blocked ) telling you yu need to update an application, never ever under any circumstances click on it.
Log out as yourself, log in as the administrator, go to the real website for that application and check / download the update from there.
This applies 10 times over for Flash & Java updates.
Turn off any auto update facilities that you have running and run the updater manually from the administrators account.
Regularly disconnect ( pull out the cord ) from the internet
Also like lawn mowers computers require some maintenance.
Defraging the hard drive is not as important as it used to be when drives had slow read/write speeds.
Rebuilding the directory is important as is repairing the permissions on macs.
Pay the extra and buy your security / maintenance soft wear on disc, never ever download it from the web, even from a site that you know to be real there are a lot of sites that spoof the real site and get between the real site & your computer so you are talking to the crooks who are pretending to be you and connected to the real web site.
Sent to you from a G5 mac tower 13 years ols & still cutting a fine lawn.