Forum on phpBB – protection against bots

Good time. There is a forum on phpBB ( sprosi[dot]club ), the hosting began overloading due to a forum filled up by bots and spam.
You need to:

The first option:

1) to remove the bot accounts and their posts
2) to protect against bots that they would not have shipped the hosting

The second variant:
Maybe you advise to migrate to another engine type, smf forum, and will transfer and setup on another engine as phpBB I have realized that not the best solution (the forum until I dead, alive people do not have)... I Will be glad Your suggestions.