Real protection requires server side code, which means an ISP that allows CGI, ASP, etc.
Since there are several different server side languages, rather than give comprehensive
solutions in this FAQ, some URLs which offer solutions/assistance are included.
gives details and C source and Perl scripts for implementing a CGI solution which outputs
the mailto tag to the browser.
An alternative method is to use code to actively look for and deny access to the spambots.
For example check the referrer and if recognised (either by IP or by agent type) take
appropriate action. This requires a list of known reprobates however and will not protect
from new spam-bots just starting up.
Spambot Beware. Detection of Spambots. Explains how to detect spambots using CGI and your raw
Spamhaus maintain a block list that can be used with server side solutions.