These things annoy me to no end. They have ruined several games for me and do nothing but serve to inconvenience all of the players. They attempt to justify that it is a "security feature", but the automatic filters are just as likely to ban people from their own accounts because it has no way to distinguish a player from a bot other than checking for a few things. Filters come in many forms, but there are all as equally annoying. They implement strict automated systems that annoy people more than they stop bots. The main problem is that customer service sucks. Just contacting them to get it resolved can take weeks sometimes.
The IP checker is by far the most annoying of the filters. Normally, it is fine because logging in from a secondary IP will just prompt you to enter an additional password and you should be able to log in once you answer that question or type in your second password. However, some games just flat out block alternate IPs from connecting to the account. Even the average modem or router does not have a fixed IP and changes between several. The checks have no way to distinguish from that. If your IP changes, then you are locked out of your old account and you will have to contact customer service to get it resolved. This becomes extremely annoying if you frequently travel between several places. Some people go from their school dorm to their school library and those usually have 2 different IP addresses. That means your account will be filtered until they get it resolved. Customer service is down on weekends and their backlog of tickets is ridiculously slow to get through.
Other games force you to enter a couple of randomized letters before logging into a game in an attempt to stop bots. This does not seem to have done anything though. Bots usually find a way to get through it in a few days and they have no problems reading the randomized letters. You would think that they would learn to stop and find a different way around it, but they do not. Their solution is usually to just add MORE capcha images. You might need one for when you log in your account, one for when you select your character, and several more while you are playing. The worst thing is that the ones that appear when you are playing are time based. That means that in the middle of a fight, you will get a pop up message that freezes your character and makes you unable to do anything while enemies can usually still kill you. The smart games will at least make you invincible during the capcha, but most games will not.