Explain firewall in network security

• This device is used for security in the network.
• It can filter data packets.
• It allows or restricts different sites.
• It can also route data packets.
• It is an OS based device.
• It can be implement at the boundary of network or in the middle of network.
• It has different types of ports like router.
• Ex – ASA 5500

A firewall can serve the following functions:

• Limit Internet access to e-mail only, so that no other types of information can pass between the intranet and the Internet.
• Control who can telnet into your intranet (a method of logging in remotely).
• Limit what other kinds of traffic can pass between your intranet and the Internet.

Firewall systems fall into two categories :-

• network-level.
• Application-level

Network-level

• It can be used as packet filter.
• These firewalls examine only the headers of each packet of information passing to or from the Internet.
• The firewall accepts or rejects packets based on the packet’s sender, receiver, and port.
• For example, the firewall might allow e-mail and Web packets to and from any computer on the intranet, but allow telnet (remote login) packets to and from only selected computers.

If you want to know more about firewall, please check on https://en.wikipedia.org/wiki/Firewall_(computing)