Introduction Of firewalls
When you use internet in your college/school/office , You may not be
access some websites, right? Do you know how they block those websites?
They use firewalls for block websites. Firewall prevent the system from
hackers attack. Lets us what is firewa
What is Firewall?
Firewall is working like a security guard standing outside the office.
Usually, What the security guard do? He will allow those who has
identity card and block those who has not the identity card. Right?
Likewise, The firewall will block unauthorized access to the system.
Firewall
may be a software or hardware. It will work based on the set of rules
defined by the administrator. Using Firewall administrator can block
certain website from being accessed.
All traffic from inside and outside of the network must pass through the firewall.
Only authorized trafic will be allowed to pass (based on the set of rules)
Types of Firewalls
Packet Filtering
Application level gate way
Circuit level gate way.
Packet Filtering (Network Layer)A
packet filtering router applies a set of rules to each incoming IP
packet and then forwards or discards the packets. Router is configured
such that it can filter incoming and outgoing packets. The packets will
filtered based on the source and destination IP address.
IP spoofing attack is possible in this packet filtering. IP spoofing can
be achieved by changing the source IP address of packets.
Stateful Inspection Firewalls
A
stateful inspection packet filters tightens the rules of TCP traffic by
creating a state table of out bound TCP connection. If the packet
matches with existing connection based on the state table, it will be
allowed. If it does not match, It will be evaluted according to the rule
set for new connections.
Application Level Gateway
Application level gateway is also known as proxy server. The user
communicate with the gateway using application layer of TCP/IP stack.
The gateway asks the user for the name of the remote host to be
connected. When the user enters valid user ID, gateway will give access
to the remote application. This will block the malicious activity and
correct the application behavior. This will ensure the safety of
company.
More secure than packet filtering. Easy to log and audit all
incoming traffic at the application level. Application-level filtering
may include protection against spam and viruses as well, and be able to
block undesirable Web sites based on content rather than just their IP
address
Circuit Level Gateway
The circuit level gateway works at session layer of OSI model.
Monitor TCP handshaking between packets to make sure a session is
legitimate. Traffic is filtered based on the session rules.
Circuit-level firewalls hide the network itself from the outside, which
is useful for denying access to intruders. But they don't filter
individual packets. This firewall is used when the administrator trusts
internal users.
Why Firewall Is Used?
Firewall block unauthorized users, prohibits vulnerable services from entering or leaving the network.
Protection from IP spoofing and routing attacks.
Protection against Remote login, Trojan backdoors, Session hijacking, cookie stealing,etc.
Limitation of FirewallsThe firewall cannot protect against attacks that by pass the firewall.
The firewall does not protect against internal threats
The
firewall cannot protect against the transfer of virus infected programs
(or) files. It would be impossible for the firewall to scan all
incoming files, emails for viruses.