You should educate yourself about computer security. There is a huge rash of malicious activity on the net right now. All the first year computer science students getting bored over the summer I suppose. Most of the code is substandard and relatively harmless, mainly annoyances. If you get one, don't panic, investigate and take steps to eradicate it. The site at http://symantec.com/
is an excellent place to get the scoop.