Wednesday night, many computer users got an unwelcome surprise from McAfee. People who had automatic update enabled received a corrupted antivirus DAT file that, upon reboot, corrupted and killed Windows XP Service Pack 3. The fix was to re-install SP3, a feat that took even competent IT professionals hours.
It is not yet known how many process control computers were affected. The total number of machines that may be affected isn't going to be known for several days, or even weeks, since the update only takes hold if the computer reboots.