Understanding firewalls

- [Instructor] While many of today's breaches result from malware being delivered through web browsing and email accounts, direct penetration through hacking is still a significant issue. A key control to prevent this is the use of perimeter firewalls. These come in two forms. Personal firewalls on endpoint devices, and enterprise firewalls to protect business enclaves. These operate in essentially the same way. A firewall in its simplest form is designed to mediate access between two computers in different zones.

Typical examples being an internal user browsing the internet. And a connection from the internet into an internal business server. To do this, the firewall has a set of rules which instructs it to either allow or deny the connection based on various criteria, such as source and destination addresses, source and destination ports, and so on. Firewalls can be built into operating systems, or can be stand-alone devices. Let's start by looking at the firewalls built in to Windows and Linux.