When I start ZoneAlarm, eg. after booting up, vsmon (according to the Windows task manager) uses about 16,000k of memory.
Leave it for a day, and it's using 50,000k. Leave it over the weekend, it's using 200,000k. Leave it for a week, and it's using 600,000k or more. Stopping and restarting ZoneAlarm resets the progression.