SPMUG 629  DSL vs. Cable
Is One Really Any Safer Than the Other?

When debating the relative merits of cable modem and DSL service,
network security might be the most controversial item on the comparison
chart. At first glance it appears one clearly wins the security battle
over the other, but does this commonly-held opinion stand up to closer
scrutiny? (See below) "What is the general consensus, cable or DSL? I'
ve heard that cable is good for now but will slow down big time when
more people sign up. Or is it the other way around?" TOKYO_GIRL


A few years ago, conventional wisdom held that DSL service inherently
offers better security than cable modem service. Some proponents of this
view happened to be DSL providers. One might dismiss such claims as a
sales gimmick from over-exuberant DSL networking companies. Yet one
finds the same sentiment among some non-commercial organizations as
well.

No matter their origins, the claims of superior security for DSL all
relate more to a perceived weakness in cable modem security than to any
unique advantage DSL might hold. Cable's Network Neighborhood

Cable modem service uses a shared cable line to provide service to an
entire neighborhood. Essentially, all cable customers in the region
belong to the same local area network (LAN). Without any security
measures in place, anybody in the neighborhood might technically be able
to click on their Windows Network Neighborhood icon and actually see the
computer names and addresses of their neighbors on the service. If a
customer enables file sharing on any drives, neighbors could even
download copies of their data!

Although some cable customers encountered this problem in the past, many
providers avoid this problem today by bundling security features in the
cable modem hardware. In particular, basic network firewall capabilities
will prevent files from being viewed or downloaded. Most cable modems
today also implement the Data Over Cable Service Interface Specification
(DOCSIS). DOCSIS includes support for cable network security features
including authentication and packet filtering [3].

DSL uses dedicated rather than shared cabling, and DSL customers in a
given neighborhood do not appear as nodes on a LAN. From this, many have
concluded DSL service provides better security. However, this argument
is at best an oversimplified one.