What is firewall? What is the use of
firewall rules in Operating System?
ANSWER
Firewall
is a network security device that is designed to block unauthorized access to
private networks. Any device that controls network traffic for security reasons
can be called a firewall. It puts up a barrier that controls the flow of
traffic between networks and is able to protect the boundary of an internal
network whilst it is connected to other networks. The safest firewall would
block all traffic, but that defeats the purpose of making the connection. The
main purpose of a firewall is to separate a secure area from a less secure area
and to control communications between the two. Firewalls can perform a variety
of other functions, but are chiefly responsible for controlling inbound and
outbound communications on anything from a single machine to an entire network.
Software Firewalls:Also called personal firewalls, are
designed to run on a single computer. They are commonly used on home or small
office computers that have broadband access. A software firewall prevents
unwanted access to the computer over a network connection by identifying and
preventing communication over risky ports. Computers communicate over many
different recognized ports, and the firewall will tend to permit these without
prompting or alerting the user. Eg.
computers access web using port 80 and uses port 443 for secure web
communications. What firewall does to block all access to the computer from any
other port, eg. Port 443 (Internet). A software firewall also allows certain
programs such as antivirus software and Microsoft Word on the user's computer
to access the Internet, if the user permits.
Hardware Firewall:This is placed between a network,
such as a corporation, and a less secure area, such as the Internet. It is more
complex and is configured using rules.
Firewall Layer rules (accept/deny)
blocks or allows specific traffic passing through from one side of the router
to the other.
Inbound rules (WAN to LAN) block all access from outside except
responses to requests from the LAN side while outbound rules (LAN to WAN)
determine what outside resources local users can have access to. Additional
rules that will specify exceptions to the default rules can as well be
applied. This can block or allow access based on the service or application,
source or destination IP addresses, and time of day. In these ways firewall
rules help guard the network and even protect the operating system from
corruption.
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