Mac OS X includes firewall software you can use to block unwanted network communication with your computer. You can use a firewall to protect all of the services available in Mac OS X, such as Personal File Sharing, Windows Sharing, and Remote Login.

Using a firewall protects the services on your computer from users on other networks or the Internet.

In addition to the firewall services in Sharing preferences, you can set additional, advanced firewall settings to further protect your computer. The advanced firewall features include:

Blocking UDP traffic

UDP (User Datagram Protocol) is a communications protocol that offers a limited amount of service when messages are exchanged between computers in a network that uses the Internet Protocol (IP). Like the Transmission Control Protocol, UDP uses the Internet Protocol to actually get a data unit (called a datagram) from one computer to another. Unlike TCP, UDP does not provide the service of dividing a message into packets (datagrams) and reassembling it at the other end. UDP is transaction oriented, and delivery and duplicate protection are not guaranteed. Blocking UDP traffic can help secure your computer.

Using firewall logging

A firewall log is a record of the your computer's activity and the data traffic into and out of your computer through a firewall. Keeping a firewall log can be helpful if you are tracking where the data is coming from and where it is going.

Stealth mode

When you enable stealth mode, all uninvited data traffic receives no response from your computer. Stealth mode virtually hides your computer behind your firewall, and other computers sending traffic to your computer receive no information about your computer.

See also