Instant messaging, the quicker-than-e-mail alternative for online communication, is moving rapidly from teenagers' bedrooms to mainstream America.
And with it, instant messaging is bringing a dark new legion of computer security problems that could eventually be worse than the worms, viruses and other Internet maladies that haunt e-mail.
Last month, the number of instant messages containing computer "malware" soared by 500 percent from the previous month, according to one Internet security company. In the first quarter of 2006, the number was up more than 160 percent from a year earlier.
Last year, security experts found 2,400 viruses, worms and other threats that hackers attached to instant messages, an increase of nearly 1,600 percent from the previous year. The programs were designed to take over computers, steal online passwords or break into computer files.
Usually, the instant messaging threats required recipients to click to a Web site that downloaded the malware onto their machines.
"What we're seeing is that the bad guys are in the process of retooling to add IM to their arsenals," said Andrew Lochart, spokesman for e-mail and instant message security company Postini Inc. "And [while] the usage of IM continues to explode in both the consumer and business markets ... there's virtually no defenses in place right now."
About 103 million people are actively using instant messaging programs such as AOL's AIM, Microsoft's MSN Messenger and others.
Only a fraction of them, however, use antivirus software designed specifically for instant messaging. Relatively few even realize that instant messages can carry the same virus threats as e-mail.
The specter of instant messaging security problems is biggest at corporations, where employees are increasingly using the service for both interoffice communications and to keep in touch with buddies about yesterday's ball game or this evening's social events.
At least 70 percent of instant messaging users have the programs at their offices, and by 2008, research firm Gartner Inc. predicts that IM will be ubiquitous at corporations.
While an instant messaging virus from a home computer might infect a few friends' machines, a virus in a corporate network can be devastating.
In April 2005, a quickly mutating computer worm infiltrated the Reuters Group PLC instant messaging service widely used by stock traders and others in the financial industry. Reuters had to temporarily shut down the system to flush it out and protect its customers' computers.
Reuters is a relatively small player in the instant messaging world. AOL, Microsoft, ICQ, Yahoo and Google, which all have free, public instant messaging services, are the biggest players.
"This is the next big thing coming," said Lisa Watts, computer network manager at the Nashville, Tenn., law firm Boult, Cummings, Conners & Berry.
Watts is so concerned about instant messaging security issues that she said she never uses the service herself. When she recently noticed some of the 300 lawyers in her firm did, she hired Postini to start filtering the messages for malware - at a cost of $3,600 a month.
"I kind of felt that IM is going to replace e-mail for threats - viruses and all that stuff," she said. "It's already started."
Other companies are taking more drastic steps.
Advanced Micro Devices Inc., the semiconductor company, prohibits employees from using public instant messaging services because of potential security problems, said spokesman Drew Prairie. Like other corporations, AMD uses a proprietary, in-house service instead, Prairie said.
In a recent survey of executives by technology research company Nemertes Research, 62 percent of respondents characterized instant messaging security as a "critical" problem.
What makes instant messaging so attractive to users is also what makes it attractive to hackers.
The service is instantaneous and seemingly more trustworthy than e-mail, letting users form on-the-spot online chat groups with designated "buddies" - spouses, co-workers, colleagues and friends.
Unlike e-mail, instant messaging doesn't require you to send a message and then wait until the intended recipient goes online, checks his or her e-mail and sends a response. With instant messaging, users can always see in a computer window which of their designated buddies are online. Instant messaging notes can be fired off nonstop - complete with attachments and links to Web sites that may or may not be legitimate.
In typical instant messaging attacks, hackers try to obtain a computer user's "buddy lists." Using automated computers, the hackers will send unsolicited instant messages to everybody on that person's list, masquerading as the person and luring recipients to check out a fake Web site.
HOW TO GET IM-MUNITY
Some tips to avoid viruses and worms attached to instant messages.
Be skeptical. Even if a message comes from someone on your "buddy" list, be suspicious if it seems unusual or prompts you to go to a Web site, open a photo file or download software. Check with your buddy to make sure he or she sent it.
Beware of unfamiliar Web sites. Even if a message seems legitimate, be cautious if it prompts you to visit an unknown site. That's how most IM "worms" work.
Use antivirus software. Antivirus software designed just for e-mails isn't good enough any more. A host of Internet security companies now also sell software that can protect corporate and consumer IM users.
Do the software updates. Many IM vendors regularly update their software to add security features. Use them.