A McAfee study of PCs around the world found that 17 percent had no antivirus protection, and the U.S. outpaced the average with 19 percent of PCs unprotected.

The study counted as unprotected machines those that had no antivirus protection installed, or whose antivirus subscription had expired. In the U.S., 12 percent of PCs did not contain any antivirus program, and 7 percent had software that was expired.