I guess you can count me among the initiated. Last month, I was subject to my first spim attack -- a crafty message, with an embedded link, that appeared to be from a friend. I soooooo should have known better. But, sure enough, I clicked and was rerouted to a page that had a whole lot of nothing.

So far there have been no adverse effects reported from my foolishness (note the lower-case f), which may be because I do all my work on a Mac PowerBook. Yet I was lucky. Many others haven't been. Among the more recent victims: users of AOL Instant Messenger (AIM).

News.com reports that on Wednesday, a malicious program called a worm penetrated the AIM network. The worm first appeared at noon Pacific time through instant messages that provided a link to a file called "picture.pif." Downloading and opening that file allowed the worm to send new messages to everyone on the victim's buddy list. Enough users did that to allow the program to spread quickly. But by 1:30, News.com says, AOL had placed a filter on its network, and the code was removed from the Web shortly after that.

The AOL attack follows a recent assault on Reuters, and new threats continue to spring up throughout the digital frontier. Indeed, according to privately held Akonix, which provides software for securing IM networks, there were more than 51 new IM attacks recorded during May. That's more than half the total of all attacks recorded during the first quarter.

Unfortunately, there's no reason to expect these sorts of attacks to subside. The startling lack of IM shielding from major vendors such as Symantec (NASDAQ:SYMC) and McAfee (NYSE:MFE) has left many users vulnerable. Protecting yourself may require double-locking the digital doors to your PC. And that means taking messages only from buddies and never, ever downloading something linked through an instant message.

For related Foolishness:

Don't take risks with your portfolio. Get better returns. Take a risk-free trial to any of our investing newsletters today, including Motley Fool Stock Advisor , which made Time Warner, the parent of AOL, one of its first selections.

Fool contributor Tim Beyers thinks worms ought to be confined to the dirt in his backyard. He didn't own shares in any of the companies mentioned in this story at the time of publication. You can find out what's in Tim's portfolio by checking his Fool profile, which is here. The Motley Fool has a disclosure policy.