Anti Splog Protection

Hi,

Today I got a splog bot that has worked around the rolling sign-up by going straight in to the register link on the login form.

Is there any extra protection against this sort of bot, apart from manually marking as spam.

95.58.228.150 - - [07/Feb/2013:13:23:03 +0000] "GET /wp-login.php?action=register HTTP/1.1" 302 20 "http://llocally.com/wp-login.php?action=register" "Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.1) Gecko/20090624 Firefox/3.5"
(that is the spambots IP address not mine - it is well tracked in project honeypot etc)