Any software designed to identify, prevent, stop and repair the damage caused by others on your computer or network can be called security software. Security software may be focused on preventing attacks from reaching their target, on limiting the damage attacks can cause if they reach their target and on tracking the damage that has been caused so that it can be repaired. As the nature of malicious code evolves, security software also evolves.
A firewall prevents unauthorized users from accessing a computer or network without restricting those who are authorized. Firewalls can be implemented with hardware or software. Some computer operating systems include software firewalls in the operating system itself. For example, Microsoft Windows has a built-in firewall. Routers and servers can include firewalls. There are also dedicated hardware firewalls that have no other function other than protecting a network from unauthorized access.
Antivirus software works to prevent malicious code from attacking a computer by recognizing the attack before it begins. But it is also designed to stop an attack in progress that could not be prevented, and to repair damage done by the attack once the attack abates. Antivirus software is useful because it addresses security issues in cases where attacks have made it past a firewall. New computer viruses appear daily, so antivirus software must be continuously updated to remain effective.
While antivirus software is designed to prevent malicious software from attacking, the goal of antispyware software is to prevent unauthorized software from stealing information that is on a computer or being processed through the computer. Since spyware does not need to attempt to damage data files or the operating system, it does not trigger antivirus software into action. However, antispyware software can recognize the particular actions spyware is taking by monitoring the communications between a computer and external message recipients. When communications occur that the user has not authorized, antispyware can notify the user and block further communications.
Home computers and some small businesses usually implement security software at the desktop level -- meaning on the PC itself. This category of security software, sometimes referred to as end-point security, remains resident, or continuously operating, on the desktop. Because the software is running, it uses system resources, and can slow the computer's performance. However, because it operates in real time, it can react rapidly to attacks and seek to shut them down when they occur.
When several computers are all on the same network, it's more cost-effective to implement security at the network level. Antivirus software can be installed on a server and then loaded automatically to each desktop. However firewalls are usually installed on a server or purchased as an independent device that is inserted into the network where the Internet connection comes in. All of the computers inside the network communicate unimpeded, but any data going in or out of the network over the Internet is filtered trough the firewall.