I'm afraid this is going to bite a LOT of people
You’re surfing the web, and you find a video that you really want to watch, (no, not one of “those” videos… well, not necessarily anyway), but it says you have to install a codec. Codec stands for compressor/ decompressor and is used to make otherwise huge video files into a more manageable size. You install the codec, and maybe you see the video, and maybe you don’t, but guess what? You’ve been rootkitted! Now, on one level, that’s just the classic bait and switch/ trojan horse scenario, but the _details_ are quite interesting.
be careful out there