John T. Smith's article: http://forums.adobe.com/thread/1321581?tstart=0 points out an issue, that is affecting many. It's basically a Trojan, but it "encrypts" files, including media files, and then demands a ransome. One method of delivery has been via CODEC's. So far, that delivery has not been associated with any specific CODEC "pack," but those have been used, in the past, to deliver nefarious payloads.
Before one is tempted to download and install a CODEC pack, I would urge the greatest of caution, before doing so.
Even some time after the MS link in John's article was dated, it appears that current anti-virus and anti-malware programs cannot detect this payload. I have seen links to "cleaners," but the upshot seems to be (as of this moment) that the encryptation cannot be reversed - yet. One might get rid of the Trojan, but the files are still lost forever.
Just a H/U, and something to think about, before installing a CODEC pack, or free CODEC, plus all the other cautions on clicking on unknown links, e-mail attachments (even if you know and trust the sender, as their computer could have been compromised, and be a zombie, spreading horrible things), or similar. Just when you thought that it was safe to go into the water...