Yes it is quite simple. You can block an IP address by using: deny from 000.000.000.000 where 000.000.000.000 is the IP address. If you only specify 1 or 2 of the groups of numbers, you will block a whole range. See http://www.freewebmasterhelp.com/tutorials/htaccess/2 or other .htaccess tutorials. You are indeed fortunate if spammer is always hitting from same IP or range of IP's. Good luck.
Shannon is right. But you will probably want to automate it. Depending on what sort of spam, comment or email, you will need to fetch their IP and write it to the htaccess file. Or within your application.