The first viruses were harmless, created in computer laboratories as research projects in the early 1980s. The first malicious viruses were spread on floppy disks exchanged by computer enthusiasts. In the late 1980s and early 1990s, Bulletin Board Systems (BBSes) became a popular means of sharing software, and thus unintentionally became a means of distributing the computer viruses that had started appearing with increasing regularity. The growth of the shareware movement and the popularity of pirated software were also helpful to virus replication.
As the popularity of desktop computing exploded and global Internet penetration rates skyrocketed in the late 1990s, the range and scope of computer viruses kept pace, especially since few of the new arrivals in cyberspace were aware of the security risks they faced. Today, there are nearly over a billion people online and more than one hundred billion email messages sent every day. Estimates of the number of viruses in circulation range from 50,000 to 500,000!