okay, you've defined the problem. i believe i know the answer, but for those who are clueless (might actually be me) , what is the solution? i'm guessing spyware, endpoint protection, etc.
anything else?
I don't do windows, can't help there. Stopped using windows a long time agom, never liked it, and tried it several times. I run linux now. People running linux here already know what to do.
Various places and online scanners and whatnot exist to help microsoft windows users, but I can't recommend any offhand, outside my current computer knowledge. Someone else I am sure though can give better advice as pertains windows. (whomever this is applicable to).
Just for a browser though, windows included, I recommend firefox with the various security add-ons, starting with Noscript.
Me, if I thought I was compromised, I would erase the hard drive and reload a known clean operating system from disk (CD or DVD) and apply all the updates immediately. I wouldn't even bother trying to find the malware, too easy for a line of code to slip through.
I would do the same with a website, but that's just me..I like simple and effective.
At home you can backup your data perhaps online, various places for that, documents/pics/vids, etc. Google docs, picasa, photobucket, flickr, youtube, etc.
Modern mac operating systems I haven't used, but again, they have some good online support forums. I used apple gear and software pre OSX, that's a long time ago now, I doubt anyone here is using like mac os 8.x stuff. (although I do once in a great while for a hoot)
HTH
I just want people to realise that compromised sites can and do daily nail people who surf through, and a lot of times they are totally unawares, and the site itself might not be aware they are compromised.
Getting good control over your javascript usage and permissions goes a long way to avoid internet cooties, with any operating system and browser combo.
For folks just finding out there are in fact more operating systems out there besides windows (like there is more than one truck or chainsaw brand..), you can go to distrowatch.com and check it out. One column on the right side has this weeks most popular distrubutions or "distros" as they are called. Linux Mint is probably the easiest and most feature rich and best support, etc, of the current batch. You (or friend or local shop or...) need to be able to download and burn an "iso" image to disk to be used to load it up.
There are walkthoughs at those various distro support forums to help. Anything in the top five or so distros will always be pretty good. I know linux mint is based on ubuntu and they do the work so that a lot more "stuff" works seanmlessly out of the box, including media playback.
The amount of free software available is downright unreal....