How can I tell if my computer is spamming the Internet?

All virus checks come back clean, I'm fully loaded with Microsoft's various healthcare products, and I'm behind a wireless router that online security tests show as being nicely locked down. But I get some spam that says I am the sender (which I assume is bogus but it makes me wonder) and once in a blue moon I get a message from some mail server somewhere that a message I have not sent has bounced.

Near as I can tell, there is no network traffic across my router when there shouldn't be, but I'm concerned about the insanity question. If you are insane, it seems likely that you would be too insane to know you are insane. Similarly, if I am infected, it seems plausible that the infection masks any clues that might lead me to realize I'm infected.

:-)

How can I tell if my computer is spamming the Internet?viruses

Most likely, the machine owned by someone you know has been hacked. This hacking read the addressbook on that machine, and sent out mail spoofed as you.

If you are interested in checking though you can download blink personal for free at http://www.eeye.com/html/index.html.

Blink will tell you what your computer is trying to send out.

How can I tell if my computer is spamming the Internet?antispam

If your computer was indeed a "zombie" and being used by someone as a spam-bot, it would be spewing out hundreds if not thousands of outgoing e-mails per hour, 24 / 7. You would therefore receive many, many, many bounced e-mail notifications, not once in a blue moon.

Relax. The black-hats are clever but not as devious as you suspect.