What is a Firewall and how does it work?

Cisco recently released their 2013 Annual Security report and the numbers are contradictory to what most people think. Cisco found that riskier links were not found on ‘shady’ sites but actually found more often on regular safe-looking sites such as search engines or online shopping sites.  In fact Cisco says that a person is 182 times as likely to download malware on a ‘safe’ site’s advertisements as opposed to a site promoting pornography. 

Have you ever asked yourself, “What prevents malware, viruses, or hackers from accessing my computer or device?” No? Well you are probably thinking about that now, and the answer is a ‘firewall.’ A firewall is a program or device designed to prevent unauthorized access to or from a private network or computer. All information passes through the firewall which examines each piece of data and blocks those that do not meet security criteria. 

There are two kinds of firewalls: Software and Hardware. A software firewall is a program you install on your computer. Software firewalls protect the individual PC it is loaded on. Each PC or laptop should have a software firewall operating on it as a safeguard. It is important for it to be loaded onto a PC because it is a secondary line of defense that protects the PC from malware or viruses that might be on flash drives or files that get thru the hardware firewall via emails.

A hardware firewall is a software driven device that is integrated into the network structure of a coporations' network. It is a physical device that works with your router and is the primary line of defense against invasions. It also gives the IT department the ability to apply restrictions on users to allow or limit access to different software programs, features sets of the software, company servers and limit access to the internet.  

Firewalls use one or more of the following methods to control traffic going in and out of your network:

Packet Filtering: The system filters each packet that enters or leaves the network and will allow or reject it based on the criteria you set for the firewall. This can be difficult to configure and is susceptible to IP spoofing (impersonating another computer system).

Circuit level gateway: This applies security mechanisms for TCP and UDP connections. Once connected packets can be transferred without additional checks.

Proxy Server: A proxy server is an intermediary between clients. Instead of one machine talking to another directly they go through the Proxy (Think of two friends that won’t speak to each other but use you to relay messages). The Proxy can be configured to have firewall capabilities and only allow certain types of traffic to pass. The only downfall is that it may slow network performance by analyzing the traffic.

Web Application: This type of firewall is a software filter that blocks data from within. For instance; Windows 7 and Vista have software firewalls that are built into the operating system. They notify you of malicious sites and downloads.

Stateful Inspection: This compares key parts of each packet to a database of trusted information. Info traveling from the firewall to the outside is monitored for defining characteristics, and then incoming info is compared to these characteristics. If the comparison reasonably matches, the info is allowed through, otherwise it is discarded.

Many firewalls use two or more of these techniques, because of the numerous ways viruses or threats can hack your system. Your firewall is considered a first line of defense in protecting private information. You need a firewall because once you are online your computer is continuously connected to the internet and identified by your IP address. It’s potentially visible to anyone on the network and malicious users may be able to gain access to it. There are many firewall options available to you so be sure to find out which one is best suited for your needs. Firewalls are a cheap way of ensuring security on your network and continuous access to the internet. Without such devices our networks would be highly susceptible to hacks and viruses, leading us to buy new systems altogether.