Audio Ads Play With No Browser Open
I have audio ads playing randomly on my computer all the time, like when all my browser windows are closed and Safari is shut down. It's not a pop-up, it's not an ad on a web page (as all windows/browsing apps can be shut down and it still happens). I get McDonalds ads, and West Virginia tourism ads, and random movie ads. What I'm trying to say is that it's completely bleeping random. They especially seem to enjoy playing at top volume while I am watching a DVD on my computer (nice to hear how awesome West Virginia is while watching Battlestar Galactica) or, even better, shouting out of my computer right as I have gotten my children to sleep at night.
I've googled it many times, and I've found a bunch of suggestions that it may be a Rootkit/bootkit kind of malware(? so says a forum commenter in response to someone's situation that sounded almost exactly like mine), but as of yet, no confirmation that this is actually the problem, and no idea of how to fix this sort of issue on a Mac (all online references to such a problem seem to be happening to people who use Windows operating systems).
It's been going on for months now, and I've hit my limit of trying to solve it on my own... Any insights?
iMac, Mac OS X (10.5.5)