I've never heard of taking the offensive against spam bots until I bumped into the site: This link kills spam
Interesting! If you find this link quite obtrusive to your site, you could just hide it through some CSS or whatnot.
For the defensive approach, here's a short list from the top of my head.
To prevent spam bots from "harvesting" your e-mail address, I've heard of:
- using images to display e-mail addresses instead of text (ex. Facebook profiles) - though it may be difficult for normal people to add you to their address book since you can't "copy + paste"
- encoding the e-mail address into it's ASCII code counterpart (so a@a.com becomes a@a.com ) - it makes the addy more difficult for the bots to read but not totally impossible...
- using alternative ways of displaying your e-mail addy (ex. myemail [at] thedomain [dot] com ) - anything will do as long as it remains readable :) )
- protecting the address through JavaScript - search query: javascript email
- Be careful when opening e-mail (even though it looks like it's coming from your friend - they may have been a victim of a phishing site or may have gotten their account hacked)
- Turn off images by default. (I'm pretty sure Yahoo!Mail and GMail has this feature.) Some e-mail may contain a web beacon (aka web bug, single pixel gif, etc. See this for more info) that is never (if not rarely) visible and sends a signal back to the sender*. These beacons tell spammers: "Hey! The mail was opened! You can send more e-mail to me since my address is active and I open spam!" Aside from that, they can collect other information such as your IP address and track usage.
