Firewalls are used to mediate and control all information
that is communicated between an external (untrusted) network
internal (trusted) network. Firewalls make use of IP
filtering and application proxies to implement firewall
Firewall is basically used to prevent the network from
Firewall are basically 2 types
1) Hardware Firewall:-Its works on network layer and used
for packet filtering usually used for network security. Its
only allow/deny packets(ports).
eg- Cisco pix, checkpoint,juniper,netgear are vendors of
2) Software Firewall:- Its work at application level.It is
signature based firewall it does not bloks malicious
packets. Its only blocks predefined malicious signature.
eg- Antivirus like Mcafee, Symantech, Quick Heal