Security Perimeter: Definition, Solutions & Devices

Instructor: Keith McNally

I have a Master of Science degree in Computer Information Systems. I have spent much of the past five years teaching computer science and networ administration.

In this lesson, you will learn the definition of security perimeter. Additionally, you will learn about the devices, equipment, and technologies used to secure a network's perimeter.

Security Perimeters in Real Life

The bad guys are out there and you know it. The thing is, you cannot see them. It doesn't matter if it's day or night - you still can't see them. But wait, your situation gets worse. The bad guys can attack you from any location: city, state, or country. It almost seems hopeless, and you are wondering what you should do! Your new boss expects you to secure the company's internal network from any outside attack. You need to move quickly and set up the correct equipment to control who, or what, can get into or out of your network.

Understanding Security Perimeters

Every privately owned network has a perimeter. The perimeter is the border between one network and another. Creating a security perimeter, then, can be defined as placing the necessary safeguards at the entrance of a privately owned network to secure it from hackers.

Network perimeter security is an essential element for any modern business whose network has access to the Internet and the World Wide Web. Just like any reasonable person would protect his or her own home from any external threat using some basic tools and common sense, the network security professional will do the same to secure a business' network from all external attacks. To do this, let's ask ourselves three basic questions:

1. How can an attacker gain access to a company's network?

2. What tools can we use to prevent an attacker from gaining access to a network?

3. What can we do if an attacker gained access to a company's network?

Understanding Access

The first question prompts us to think about network access and the type of person trying to gain that access. Let's address the last part first. Who might be trying to access a company's data illegally? A hacker is a person who tries to gain illegal access to a company's data by using electronic means, such as the Internet.

Now that we know who is trying to access someone else's information, we need to consider how they can do it. We will use your home as a comparison to a company's network. Your home might have more than one entry point. These would include the front door, the back door, and any visible windows.

A company's network typically has one entry point. This entry point is called the edge router, the device in which all network traffic must pass in order to get into the network. And just like you would use one or more locks on your front door, you would apply one or more locks on the edge router. These locks are called access controls, and they would all be included on an access control list. People are more familiar with the term firewall, but technically it's the same thing. The firewall, or access controls, is used to manage the traffic into a network.

Preventing Access

The second question prompts us to think about the equipment and technologies that we can use to prevent a hacker from gaining access to a network. Well, just as people might set up an alarm system in their own home to detect sound or motion, the same can be done for a network. At home, your detection system will alert you to any changes in motion or noise. Additionally, if you are not home, and someone cracks the front/back door open, an alarm will sound, the police will be called, and the detection service will give you a call on your cell phone.

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