It's a frequent thing to find malware on macs that come through for repair these days.
Symptoms can include a general system slow down, programs that pop up shortly after you login, perhaps random web pages opening when you click on a link, or you may even find a web page stuck in full screen mode with no easy way to close it.
How did it get on your system?
Well, someone downloaded something they weren't meant to, or downloaded a legitimate program from the wrong site, or were tricked into downloading a program like Adobe flash, when in fact it was an add that imitated the usual adobe flash update that comes through every second week or so.
The key to remember is when downloading a program, only do so from the author's website, get Skype from Skype.com, get flash updates only from Adobe.com etc. As soon as you enter your mac password, the downloaded program (legitimate or not) has open access to install whatever it wants, and this can include bonus malware, browser extensions, bogus backup or optimisation programs etc.
If you suddenly find your search engine is Yahoo, chances are you have malware on your system.
There are a few programs that can identify infections and remove them, but the more severe malware needs specialist removal and there are only a few people on the Gold Coast that can do this for you - and the genius bar is not one of them.
Don't be concerned about cost, even the most difficult mac infections can be professionally removed in around 30 minutes by us.
What I would highly recommend is bringing any infected macs in for malware removal before using them for internet banking. We have personally seen fraud occur on clients infected macs due to keystroke malware recording and sending bank login details to hackers. It is happening and for that reason you must be vigilante. For the sake of $50 be sure your system is infection free and book in your mac for a quick service when you have 30 minutes spare.
Wishing you happy and safe computing.
Unit 8, 14 Rothcote Court Gold Coast BURLEIGH HEADS QLD