1. "As a general rule, be extremely wary of URLs ending in '.jpg.html' and '.scr,' as in many cases the harmful software is being hidden at locations that end with these extensions."  Information not every gamer knows about, to be sure, so URL checking is always a smart thing to do with sites you don't know or trust.
2. Secure your computer. Most of you probably already have something like this, but it still bears mentioning every so often. Get yourself strong firewall and antivirus programs and keep them updated. If you're not that tech savvy, it would be a good idea to talk to someone who's good at IT and computer protection. These precautions aren't perfect, but they do help.
3. Use the Blizzard Launcher. Sure, it can be slow as hell to download a patch this way, but since Blizzard already adapted the technology to work with updating the game and only the game, there's a lot less to worry about. Now, you could wait for someone you know who's got the best protection and already downloaded the patch for uploading onto a file upload site, but his security's already compromised, you could be in trouble as well.

Via World of Warcraft