Bots arnt always bad. If they arnt posting or joining then theyre indexing your site for search engines like google. These Bots are normal and most likely followed a link to get to your site, either form here or maybe even your host.
Oh, btw, unless you really have "ChatZone" trademarked, id take off the TM. No point getting sued.
Are they bots as in bots recognised by phpBB as being search bots or spam bots signing up or guests which are obviously bots?
If they are bots that are guests and have a distinguished useragent such as some of one that used to hit FP which all had useragents like libwww-perl or Python-urllib then you can block them through your htaccess file which is what i have been doing here as some of these bots especially the libwww-perl ones were hitting us quite hard and sometimes there would be 20 of them viewing the forum at exactly the same minute.