From Robert Lemos’s Plague carriers: Most users unaware of PC infections (CNET News.com: 25 October 2004):
A study of home PCs released Monday found that about 80 percent had been infected with spyware almost entirely unbeknownst to their users.
The study, funded by America Online and the National Cyber Security Alliance, found home users mostly unprotected from online threats and largely ignorant of the dangers. AOL and the NCSA sent technicians to 329 homes to inspect computers. …
Nearly three in five users do not know the difference between a firewall and antivirus software. Desktop firewall software regulates which applications on a PC can communicate across the network, while antivirus software detects malicious code that attempts to run on a computer, typically by pattern matching. Two-thirds of users don’t have a firewall installed on their computer, and while 85 percent of PC owners had installed antivirus software, two-thirds of them had not updated the software in the last week. The study found one in five users had an active virus on their machines.