A firewall is every bit as critical to security as an anti-virus program. Firewalls stop malware from spreading to a network and defend against hackers attempting to infiltrate a targeted system. Disabling a firewall can therefore leave a business vulnerable to abuse, allowing viruses to infect interconnected devices, and giving cybercriminals the opportunity to execute malicious code remotely.
Basics
Businesses can implement two different kinds of firewalls: software firewalls and hardware firewalls. The former is installed to an individual computer and protects that particular host from threats, while the latter acts as a bridge between a local area network and wide area network, protecting all of the devices attached to the LAN. Hardware firewalls can be standalone devices or integrated into a router. Hardware firewalls block ports and restrict incoming traffic, while software firewalls provide a more thorough defense, limiting not just what traffic enters a LAN, but also what traffic leaves it.
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Effect
Disabling a firewall permits all data packets to entering and exiting the network unrestricted. This includes not just expected traffic, but also malicious data -- thereby putting the network at risk. If a software firewall is disabled, it's not just the associated computer that's in harm's way; worms -- a type of malware -- for example, can spread across a network connection, infecting all of the PCs attached to the LAN. Disabling a hardware firewall also impacts all of the devices that connect to the network.
Alternatives
Since firewalls control incoming and outgoing connections, problems can occur when attempting to use certain applications or services that require Internet access. To enable these programs to use the Internet, you can open the appropriate ports in the firewall without turning off the firewall altogether. Some programs use a pre-defined port or range of ports, while others allow users to manually configure which port or ports the software utilizes. Opening the firewall does potentially allow malicious traffic to enter through the applicable port, but businesses can use nonstandard ports, when possible, to reduce the risk of attack.
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Considerations
Sometimes, to perform certain administrative tasks -- like applying software updates or installing new programs -- the software firewall must be disabled. When possible, administrators should disconnect a computer from the Internet before disabling the firewall to eliminate the risk of attack. Depending on the program, you can schedule the firewall to reactivate after a certain amount of time has passed or after the system has been restarted.
