I have created a new, relatively simple rule that traps most of the new image spam and virus-enclosure email messages in their tracks, so I thought I'd share. In Mail, create a new rule (in Mail -> Preferences -> Rules), with this setup:

• Choose All on the conditions line.
• Change the first condition line to: Any Attachment Name - Contains - then type a period in the last box.
• Click the + button to add a second condition, and set it to Sender is not in my Address Book.
• Set the Action for this new rule to Move message to mailbox Junk.

I know it seems simple, but it's been very effective in stopping the new breed of image spam *and* all of those spam messages with an enclosed .pif file. Rather than picking through over 100 emails per day in my inbox, I just scan the mail in the old Junk folder and delete them all in one step.

[robg adds: This should work well for most people, who tend not to receive attachments from non-regular correspondents. If, like me, you do receive such attachments, you might wish to modify the 'attachment contains' portion of the rule -- specify .PIF, for instance, instead of just a period.]