Also called the application level gateways, Proxy Server Firewalls are the most secured type of firewalls that effectively protect the network resources by filtering messages at the application layer. Proxy firewalls mask your IP address and limit traffic types.

Firewall rules should be documented, tracking the rule’s purpose, what services or applications it affects, affected users and devices, date when the rule was added, the rule’s expiration date, if applicable, and who added the rule. A good firewall policy also has a formal change procedure to manage change requests.

Here are some of the more common ones:

• IP addresses – filter out traffic from suspicious IPs.
• Domain names – block traffic from known malicious domains.
• Ports – deny traffic trying to enter through a certain port.
• Contents – block data packets containing certain keywords.

As the most “basic” and oldest type of firewall architecture, packet-filtering firewalls basically create a checkpoint at a traffic router or switch.

Advantages of Firewall

• Monitor Traffic. A major responsibility of a firewall is to monitor the traffic passing through it.
• Protection against Trojans. Malwares especially the type Trojans are dangerous to a user.
• Prevent Hackers.
• Access Control.
• Better Privacy.

The main disadvantage of a firewall is that it cannot protect the network from attacks from the inside. They often cannot protect against an insider attack. Firewalls cannot protect a network or pc from viruses, Trojans, worms and spyware which spread through flash drives, potable hard disk and floppy etc.

A firewall cannot prevent users or attackers with modems from dialing in to or out of the internal network, thus bypassing the firewall and its protection completely. Firewalls cannot enforce your password policy or prevent misuse of passwords.

We recommend replacing your firewall every 3 to 5 years. As mentioned above, your firewall should be updated as often as security updates and patches are released for it. Just like computer operating systems, firewalls reach an end of life date. After that date no more security patches and updates are released.

Generally, the hardware for a firewall will start somewhere in the $700 range for a very small business and can easily get into the $10,000 range. However, most business sized 15 to 100 users can expect the hardware of the firewall to cost between $1500 and $4000.