Zone Alarm found at least five viruses during backup to another hard disk. But ZA is always running on my computer, definitions updated daily, scanned weekly, for years. Any ideas how ZA could have missed these viruses all this time, especially the one in Eudora (which I haven't used for years)?

One virus was found in ...\Eudora\attach\UntitledBO
Another three in ...\Application Data\blinx\filescan\newmail_1252 (etc.)
One Trojan in \Device\Harddisk Volume Shadow Copy 1\Docs\Settings\[User name]\Application\Trojan-Spy.html.Fraud.gen

Operating System:Windows XP Home Edition
Product Name:ZoneAlarm Internet Security Suite