How Does a Firewall Prevent Break-ins?
Personal firewalls protect against external attacks by limiting access to doors. When a program opens a door on a computer, it is the responsibility of the program that opened the door to control access and limit the ability of visitors to do harm. There are several reasons this may not happen. Among them: • The program may have a defect allowing visitors to do unintended things. Unfortunately, this is a common problem and is responsible for many computer break-ins. To help avoid this scenario we must update our programs regularly. • The program may be fooled into thinking the visitor is someone we authorized to use the door. For example, the visitor may have discovered the authorized person’s password or spoof a computer address we’ve allowed to use the door. • The program may be misconfigured by the operator or be shipped in a vulnerable configuration. • The program may simply be too trusting in its design. It may have been designed with a trusted network in mind while it, in fact, r