If you have either of the internal DSL cards (the Intel 2100 or the Cisco 605), Bridging and PPP doesn't make a difference as far as security or networking. You should treat your computer as though it is in Bridging mode.

If you have the external Cisco 675, then which mode it is in does make a difference.

Bridged Ethernet (Bridging)
StarNet has used bridged ethernet since it first started offering DSL. In this mode, the Cisco 675 is basically a "dumb" networking device. All it does is pass information on to Qwest's DSL network (and then to StarNet) and pass information from the Internet to the computer or computers hooked up to the Cisco.

In this setup, each computer hooked up to the DSL line is directly connected to the Internet. "Directly connected" means that the computer contacts computers on the Internet itself and receives replies directly back from the Internet.

This has certain advantages, but in Internet security there is a saying, "If you can access something directly, then there's the chance they can access you."

In this type of connection, it is rather important (as far as security is concerned) to follow the steps for individual computer security.

As far as networked computers, an IP address is a unique identifier used in TCP/IP (the protocol used on the Internet and some local networks). In Bridging mode, the IP address for all the computers connected to the Cisco are provided by StarNet's DHCP server. The IP address for any specific computer could change at some point. If you are using TCP/IP for a local network as well as Internet access, changing the IP address could cause the local network to become confused.

PPP
StarNet has been taking volunteers to switch to PPP. This mode is better understood and better supported by the hardware manufacturers. StarNet has noticed significant problems related to having a large number of customers in Bridging mode, and thus is considering switching to primarily PPP mode.

Again, if you have the internal DSL equipment (the Intel 2100 or the Cisco 605), then there is no real difference between PPP and Bridging mode.

If you have the Cisco 675, there is a difference.

In PPP mode, the Cisco 675 is the only device that could be considered directly connected to the Internet. All computers that are connected to the DSL line send their request to the Cisco 675. The Cisco passes on the request and then routes it back to the requesting computer.

As far as security is concerned, PPP is superior to Bridging. All the computers hooked up to the Cisco. None of the computers are directly connected to the Internet. Since the computers cannot access anything directly on the Internet, it is virtually impossible for anything on the Internet to directly access the computers.

Computers connected through a Cisco 675 in PPP mode can rest a little easier, as far as security. It will still be a good idea to look into individual computer security.

As for networked computers, the computers connected to the Cisco still get assigned IP addresses, but they are special addresses that will only work on the local network (not the Internet). These IP addresses are assigned by the Cisco 675. So, as long as the Cisco is on, the IP addresses for the individual computers won't change. There is also the option to assign the special IP addresses to each computer and not use the Cisco for that at all.