Hey AMD,
Welcome to PCHF.
I know exactly what your talking about. SPAM filters cannot detect them because pictures are used instead of text, therefore nothing to filter. It usually starts with a single infected PC, most likely a friend using Outlook Express. The infected machine will read the Address Book and pass those e-mail addresses on. There is absolutely no way to stop these e-mails except to use a whitelisting SPAM filter such as SpamJab (
spamjab.com: Protecting families from Spam), or to change your e-mail address completely.