Each player in the game has a limited number of available raid attempts per day. However, you can face with a situation when a player raids your City over the established limit and sends a lot of consistent attacks. It can be done without any cheats, hacks and tricks.
The thing is that when you reach the limit of available raid attempts, you will still be able to raid other Cities. However, the raids you send over the limit will be sent as regular attacks. I.e. the troops will attack your opponent's City, fight with the enemy's troops, but will not bring you plundered resources if the raid is successful.
Multiple successive attacks are considered as normal game process and are not a violation of the regular gameplay rules. You can always protect your City using Full Protection item, defend your City with your troops or with reinforcements.