When you are in control of a network system that houses more than several people, you have to be able to think about a lot factors that can affect that network. When you are on a smaller network the amount of attacks that happen to you will be less. But when you are on a medium to large network you have to worry about all type of attacks that will come at you. And you have to be prepared to respond accordingly. If you are not prepared then the bad guys will eventually come and tear your system up.
One of the ways that you can keep prepare is setting up your system against known security tactics. You want to try your best to make it harder for the bad guys to be able to get in your system. You do this by not making anything easy for them. For black hat hackers, easy means that they are able to attack your machine with an older attack and a more wide known attack. If your system gets hit with a new attack that there is no way that you could have saw coming, then it is not really your fault. But if your system is hit by an attack that is well known and which could have been prevented then it is your fault and you can expect to be in trouble.
The first type of attack that you should be ready for is the Brute force attack. This is attack that takes the entryway of your network and tries to guess the password. The machine keeps trying and trying until it is able to come up with one. This is one of the oldest types of attacks in the books but it unfortunately still works too many times. And with the average black hat hacker having access to stronger computers, the attacks are going to happen a lot more often.
You can easily stop an attack like this by first limiting the amount of times a person is able to try and guess the password combination. After a few times of missed guesses they are locked up for an hour or so. Also you can prevent this by having a proper password procedure. Make sure that no one on your network has an easy to guess password.