Just saw this posted on another forum. It's very short, and worth a look if you use IE as your main browser...
http://www.codingforums.com/showthread.php?p=354125#post354125
edit: they've removed the link - perhaps it's for the best. In short, somebody posted the source code for a page that when opened, would present you with a popup box you couldn't get out of without task manager unless you clicked yes. Clicking yes ran the rest of the vb script which ran command line instructions on your computer. In this case, it was t warn you that the computer would shut down in 100 seconds because you'd been 'hacked', and then your coumputer would shut down.
I didn't test it, but it looked like it would work, and it's now been removed so I assume it would. Not nice.
http://www.codingforums.com/showthread.php?p=354125#post354125
edit: they've removed the link - perhaps it's for the best. In short, somebody posted the source code for a page that when opened, would present you with a popup box you couldn't get out of without task manager unless you clicked yes. Clicking yes ran the rest of the vb script which ran command line instructions on your computer. In this case, it was t warn you that the computer would shut down in 100 seconds because you'd been 'hacked', and then your coumputer would shut down.
I didn't test it, but it looked like it would work, and it's now been removed so I assume it would. Not nice.