The US Pentagon computers are the targets of an average of 400 probes a week, with about 60 defined as "attacks." The US Department of Defense and NATO command announced recently (May 1999) that their computer networks were sabotaged into a "denial of service" after Serbia-based hackers bombarded them with virus-laden e-mails. Three US government sites - the Energy Department, the Interior Department and the National Park Service - were hit by people protesting NATO's bombing of the Chinese Embassy in Belgrade, forcing them to shut down their home pages for a day. The hacking was traced back to China.
The Melissa virus first appeared on the Internet in March of 1999. It spread rapidly throughout computer systems in the United States and Europe. It is estimated that the virus caused $80 million in damages to computers worldwide. In the United States alone, the virus made its way through 1.2 million computers in one-fifth of the country's largest businesses. US citizen David Smith pleaded guilty on December 9, 1999 to state and federal charges associated with his creation of the Melissa virus.
The "Love Letter" worm was a malicious VBScript program which was spread in a variety of ways on May 4, 2000. More than 250 individual sites were affected indicating more than 300,000 individual systems were affected. Sites suffered considerable network degradation as a result of mail, file, and web traffic generated by the "Love Letter" worm. The "Love Letter" worm infected systems via electronic mail, Windows file sharing, IRC, USENET news and possibly via webpages. The worm executes by sending copies of itself using Microsoft Outlook to all the entries in all the address books. The worm searches for certain types of files and replace them with a copy of the worm. Executing (double clicking) files modified by other infected users results in executing the worm. Files modified by the worm may also be started automatically, for example from a startup script.