Spam bots are probably finding the user URL (<a href="http://example.com/user">http://example.com/user</a>) and the subsequent &#39;create account&#39; link. <div><br></div><div>You need to prevent anonymous users from creating accounts.<div>
<br></div><div>In Drupal 6 visit admin/user/settings</div><div>In Drupal 7 visit admin/config/people/accounts<br clear="all"><div><br></div><div>Alternatively, if you do wish to have anonymous users create accounts but prevent spam, you could add a captcha to the account creation form.</div>
<div><br></div><font color="#333333">Carl Wiedemann</font><div><div><font color="#333333">Website design and development consulting</font></div><div><font color="#333333"><a href="mailto:carl.wiedemann@gmail.com" target="_blank">carl.wiedemann@gmail.com</a> | skype: c4rlww</font></div>
</div><br><br></div></div>