Firewalls

• A firewall is a network security system, either hardware or software based that controls incoming and outgoing network traffic based on a set of rules.
• Firewall technology developed in the late 1980s.





• Firewalls work like a filter between your computer/network and the Internet.
• You can program what you want to get out and what you want to get in. Everything else is not allowed.

Types of firewall

Packet/network firewalls

• These are the earliest firewalls functioned as packet filters, inspecting the packets that are transferred between computers on the Internet.
• When a packet passes through a packet filter firewall, its source and destination address, protocol and destination port number are checked against the firewall's rule set.

Stateful firewalls

• These firewalls used to recognize a packet's connection state.
• First introduced in 1994 by Check Point Software.
• The additional information can be used to grant or reject access based on the packet's history in the state table, and to speed up packet processing.
• So the packets those are part of an existing connection based on the firewall's state table can be allowed through without further analysis.

Application layer firewalls

• These firewalls protect servers and the applications running on them, not the network resources behind them.
• This technology first developed in 1999.
• These firewalls inspect and filter packets on any OSI layer up to the application layer.
• These firewalls have ability to block specific content, such as known malware or certain websites, and recognize when certain applications and protocols being misused.

Proxy firewalls

• A proxy firewall is a network security system that protects network resources by filtering messages at the application layer.
• Proxy firewalls are considered to be the most secure type of firewall because they prevent direct network contact with other systems.
• A proxy firewall acts as an intermediary between in-house clients and servers on the Internet.

Advantages

Monitors traffic

• At the time of transmission of packets through the network firewalls investigates to determine whether they something contain that's potentially hazardous to your network’s security.

Block Trojans

• A firewall helps block Trojan horses.
• Trojans are specially dangerous because they silently transmit what they uncover about you to a Web server.

Stop hackers

• Having a firewall keeps hackers out of your network.
• Without firewall security, a hacker could get a hold of your computer and make it a part.

Stop key loggers

• Having firewall security will reduce the risk of key loggers monitoring you.
• A key logger is spyware software that cyber criminals try to put on your computer so they can target your keystrokes.
• So they can know what you are typing, and because of this information they can access your private account.

Disadvantages

• Firewalls can degrade your system performance, because it's a demanding task to examine every packet of data.
• Configuring and maintaining of firewalls are difficult.
• Sometimes difficult to remove or uninstall a firewall completely.

Examples

My notes