We've seen worms evolve over the years. Over the past year, we've seen several that try to use social networking sites to assist in their propogation, whether it be through account hijacking, fake accounts or some other information manipulation. YouTube is now one of the latest vessels that malware is using to spread, with a harmless video being used to entice users into clicking a link.
The video itself is harmless, and YouTube itself isn't the issue here. However, the video also has links in its page - just like any other YouTube video can have. Of course, the link results in infection if your machine isn't up to snuff or you are being a little too gullible:
Watching the You Tube video is safe. The danger comes at the end when the video displays a site where you can download the game mod itself. Should you download the file and install, your computer will be compromised upon reboot.
What is most interesting is that it isn't being spread by any automated means - people are locating the video and passing it along to other sites, blogs and forums around the web. An aura of trust is created when many people are participating, one that can lead many into a false sense of security.
The weakest link is always going to be the human one in the chain of computer security. Be careful when you browse. You can get more information on the virus in question at the SpywareGuide site.