so i have a subdomain. and i was wondering if i was allowed to ban people? or does your host have to do that for you?

You can give your admin the ip address and ask them to ban them.
Heres some links with codes to do it though.
http://forums.digitalpoint.com/showthread.php?t=67344
http://www.htmlbasix.com/blockusers.shtml

toolator.com works for me. It "bans" through redirecting though.

as long as you have to option to do that and its not against any of the admin terms then its good.

if you know the IP address of the person you're looking to block, you can just use a simple rule in a .htaccess file.
if you don't already have a .htaccess file, you'll need to create one (the entire file is named ".htaccess"; there's nothing before or after it).

paste this into the file, save it, and upload it to the root directory of your domain (yoursite.yourhostsite.com/.htaccess):
replace the # symbols with the IP address. if you need more, just add them to the list.