You probably know those mails that tell you that a legal investigation has been started against you because child pornography has been found on your computer. When you open the attachement, a trojan will be installed.
Well, those kind of mails sometimes have a good side: A child pornographer turned himself in to the police in Germany after having received such a mail.....
Read the whole story: http://news.yahoo.com/s/nm/20051220/wr_nm/crime_germany_worm_dc
Viruses are not always bad :-)