Yes, it is definitely possible to block by IP address, but here are the downsides of doing that:
hackers and spammers can change their IP addresses quickly and easily (this is completely automated) on the fly.
There are literally millions of hacker and spammer IP address out there so it can become an ongoing time consuming task to block by IP addresses.
We have done extensive testing with IP blocking in this Forum Topic link below.
http://forum.ait-pro.com/forums/topic/buddypress-spam-registration-buddypress-anti-spam-registration/
See this forum topic link for more explanation about why blocking by IP addresses is completely ineffective and a waste of time: http://forum.ait-pro.com/forums/topic/blocked-attempts-but-no-automatic-blocking-of-ip/#post-24854
While the IP address blocking method is fairly effective it is an ongoing process that is time consuming to do. If you skip to the very last post in that Forum Topic you will see that by using a CAPTCHA based deterent for spammers vs an IP blocking deterent we have almost zero spam registrations on this Forum site, where with IP address blocking we were still getting new spammer registrations on an ongoing basis and had to keep adding new IP addresses to block those new spammers.
BPS Pro will have CAPTCHA Anti-Spam options in BPS Pro 7.1. We are in the final testing phase of CAPTCHA Anti-Spam development right now and are close to final production release. We do not have an estimated time of completion for BPS Pro 7.1 yet.
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