This can lead to damage of important data ,or the whole network. So the solution isn’t to cut off the network from internet, Instead we can build firewalls to protect the network.

A firewall is a software running on  another computer. which inspects the network traffic through it, and denies or permits pasage based on a set of rules. A firewall’s basic task is to regulate some of the flow of traffic between computer networks.

A firewall can be implemented both in hardware and software, or a combination of both. Firewalls are frequently used to prevent unauthorized internet users from accessing private networks connected to the internet, especially intranets. All messages entering or leaving the intranet pass through the firewall,which examines each message and blocks those that do not meet the specifies security criteria.

There are several types of firewall techniques:

• Packet filter: It looks at each packet entering or leaving the network and accepts or rejects it based on user-defined rules.
• Application gateway: It applies security mechanisms to specific applications such as Telnet servers.
• Circuit-level gateway: It applies security mechanisms when a TCP or UDP connection is established.Once the connection is made,packets can flow between the hosts without further checking.
• Proxy server: The proxy server is a application program which services the requests of the clients by forwarding requests to other servers. The proxy server hides the true network address.

You can download it from WindowsVJ.com.

Here is the link : Windows 7 : Tips& Tricks PDF Download Size : 5.8 MB

Also this Ebook is available in XPS format. Windows 7 : Tips& Tricks XPS Size : 6.44 MB

1. Position your wireless router (or wireless access point) in a central location
When possible, place your wireless router in a central location in your home. If your router is against an outside wall of your home, the signal will be weak on the other side of your home. Don’t worry if you can’t move your router, because there are many other ways to improve your connection.

2. Move the router off the floor and away from walls and metal objects (such as file cabinets)
Metal, walls and floors will interfere with your router’s wireless signals. The closer your router is to these obstructions, the more severe the interference, and the weaker your connection will be.

8 more tips here http://tech.msn.com/microsoft/article…