Unless the machine is a Macintosh, a firewall (either a firewall router, a software firewall, or both), is very
much a necessity, whether on broadband cable or DSL.
Otherwise, the (Microsoft O.S.) machine risks being unknowingly hijacked as a "zombie" spam email sender.
An anti-virus program and 2 or 3 anti-spyware programs (such as Microsoft Anti-Spyware) are also
practically mandatory.