Do you mean showing up in the 'who is on line' as guests or actually posting?
Bots will index your forum the same as any other website. If you have a particular bot in your memberlist with the correct permissions you will be able to see who that are, what they are doing and allow/disallow them to view certain areas.
If the bot is not a member, then it can browse the forum as any guest would.
Remember, Bots ane SPAMbots are not the same thing.
To deal with SPAM please read the following:-
Please visit Preventing Spam in phpBB3
for various options for fighting spam in phpBB.
How to configure Q&A
- Administration Control Panel (ACP) > Spambot countermeasures> Installed plugins > click the dropdown box and select Q&A (it will be greyed out)
- Click the configure button then click add
- Add your question and answer (you need a Q&A for each language you have installed) click submit
- Click "back to previous page" then click "back"
- Select Q&A from the dropdown box (again)
- Click submit at the bottom of the page.
The link to your forum results in a 'not found' so I am unable to look at it for you