Some 23 percent of the 237 million computer system attacks made in the first half of 2005, were directed as U.S. government computers. Spam, and nuisance (as opposed to destructive) viruses declined. More of the attacks had clear criminal intent. Most of this was your basic frauds, extortion and theft (of information.) The number of emails carrying dangerous payloads (like a virus) went up from about two percent 18 months ago, to three percent a year ago, to about four percent now. While various bits of defensive software (spam filters and the like) stop most of these malicious messages, some get through. Not only that, but the increase in malicious messages can be traced to the increased participation of criminal organizations. In the past, most of the bad stuff being tossed around was from geeks gone bad (young guys with too much time on their hands, and Internet access). Now people are out to make a buck. You also have  intelligence agencies out looking for information. Many attacks against government computers appear to be concentrated, and out for specific types of information. The big problem is that the only intruders you catch are the less skillful ones. The really good ones get in, get what they want, and get away without ever being detected. U.S. Department of Defense computer security experts know for sure this is how it works, because they have pulled it off on foreign computer systems. They have also found out about some network penetrations, long after the fact, from informers. Theres no reason to believe such attacks are not still being directed at Department of Defense computers. Actually, its not a matter of if its being done, but how much.