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I have a desktop computer manufactured by Dell. I use Windows xp O/S . I do not know much about computer systems as I belong to a commercial field but I know a few things about viruses and their ill effects. I think a Windows O/S provide a firewall to protect this unwanted viruses. But what is packet filtering, many network protocols use packet filtering to prevent the virus attack. Can anyone please explain what sort of packets are being filtered in here?
As we know very well that a firewall is placed between the outside netwrk and the internal host. The internal host computers and and the outside network transfer the data in form segments sometimes called as packets.These packets are of definite size depending upon the networking protocol being used. These packets does not flow directly, but it has to pass a set of rules. If the packet passes and matches the set of rules being set then it is allowed to pass, otherwise rejected. This Firewall can be set in different forms Circuit Switching, Proxy Server and Packet Filtering.
Yes you are absolutely correct, there are set of rules and regulations which the ongoing packets must follow. These rules are called as filtering rules. The packet filtering allows or restricts packets on the basis of their machine or port number. These packet filtering is also done in two ways: Static filtering in which the entry or exit of all the packets is allowed from or to only a specific ports assigned by the administrator.On the other hand Dynamic packet filtering allows only a certain users rest all are restricted.
That was all about packet filtering . There are filtering norms too .We can do the filtering on the base of address i.e to prevent the internal host from sending the packet to a particular MAC address or IP address or stop the packet entering from a restricted IP address. The filtering can also be done on the basis of type of data. In the firewall settings we can block the packets of too large or too small size.The packets can also be prevented on the basis of their format such as prevent .GIF files .