short, cryptic email messages

Once every day or two I get short, anonymous, cryptic email messages, like...
"Is this you?"
"Confirm your password."
"I'm waiting."
...and such. Each has a .zip attachment, but I don't open them, for fear of introducing a virus to my computer. Back in the beginning I did open one, but it contained gibberish. Each is from a different email provider, too, like ntsonline, etc. I use a Mac, OS 9.2.2, Internet Explorer 5, Outlook Express 5.02. These don't seem to damage anything. They're just pesky and insidious. Are they viruses? Can I do anything to track them to their source, or eliminate or block them?

Thanks,

Tom in Texas

Can't be 100% sure they're viruses but it's quite likely.  My rule of thumb is, if you don't know the person and didn't request the file then you don't want or need it.

There are programs that can filter E-mail. Mailwasher for example:

http://www.mailwasher.net/