I am, personally, a recipient of 2 of these nasty PMs going around, and just wanted to warn you. Here's a couple tips on how to avoid them:

1. I've noticed that both senders of those PMs had bad grammar, capitalization, and spelling. Don't open a message with any/all of these mistakes, especially if you know that member not to make those mistakes.
2. Really, don't open a message you're not interested in. I'd rather not open a message than risk seeing those horrible pictures again.
3. Try to avoid PMs from people you've never heard of. Unless you're really interested in it.
4. If you get a message from a non-staff member saying +/- PE, DO NOT OPEN IT.

1. Click 'reply'
2. Copy the image's web address
3. Paste it in a new window
4. Then, go to the member's profile
5. Click on a link to a picture in one of the member's topics
6. If the two image hosting sites match up, it's most likely not a hacker. If they don't, it most likely is.

For more help, read some of the comments.