Mitel WRV54G 사용자 설명서

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Chapter 3: Planning Your Virtual Private Network (VPN)

Computer networking provides a flexibility not available when using an archaic, paper-based system. With this 
flexibility, however, comes an increased risk in security. This is why firewalls were first introduced. Firewalls help 
to protect data inside of a local network. But what do you do once information is sent outside of your local 
network, when e-mails are sent to their destination, or when you have to connect to your company's network 
when you are out on the road? How is your data protected?

That is when a VPN can help. VPNs are called Virtual Private Networks because they secure data moving outside 
of your network as if it were still within that network.

When data is sent out across the Internet from your computer, it is always open to attacks. You may already have 
a firewall, which will help protect data moving around or held within your network from being corrupted or 
intercepted by entities outside of your network, but once data moves outside of your network—when you send 
data to someone via e-mail or communicate with an individual over the Internet—the firewall will no longer 
protect that data. 

At this point, your data becomes open to hackers using a variety of methods to steal not only the data you are 
transmitting but also your network login and security data. Some of the most common methods are as follows:

1) MAC Address Spoofing

Packets transmitted over a network, either your local network or the Internet, are preceded by a packet header. 
These packet headers contain both the source and destination information for that packet to transmit efficiently. 
A hacker can use this information to spoof (or fake) a MAC address allowed on the network. With this spoofed 
MAC address, the hacker can also intercept information meant for another user.

2) Data Sniffing

Data “sniffing” is a method used by hackers to obtain network data as it travels through unsecured networks, 
such as the Internet. Tools for just this kind of activity, such as protocol analyzers and network diagnostic tools, 
are often built into operating systems and allow the data to be viewed in clear text.

3) Man in the middle attacks

Once the hacker has either sniffed or spoofed enough information, he can now perform a “man in the middle” 
attack. This attack is performed, when data is being transmitted from one network to another, by rerouting the