Limit rate of login attempts and block IP temporarily. It is protecting from brute force attacks. Login lockdown system.
The most advanced protection against sploggers and spam users registration, is fully WordPress,WordPress MU ,BuddyPress and bbPress 2.0 compatible
Spam Master is the Ultimate Spam Protection plugin that blocks new user registrations and post comments with Real Time anti-spam lists.
To block users from admin side except admin users for specific day,time, and date or permanently.
Limit Attempts Booster is a wordpress plugin which provides high security and limits your wordpress access. It also safes from brute force attacks.
Allow members of the forum to selectively have a user's posts and topics hidden from view.
Block or Delete spam user on Registration by email domain & username.