Transmission security issues

["Dan Lynch" <dan.lynch () placer ca gov>]

Greetings list,
 
What specific differences exist between the following transmission
networks that affect the security of data crossing them:
 
1) a home user's DSL-based internet connection
2) point-to-point T1 leased from a major provider
3) dark fiber capacity leased from a cable TV provider or local telco
 
In all cases the traffic leaves your zone of explicit control and
enters a provider's "cloud". Why do we consider numbers 2 and 3 more
secure than 1? As a hypothetical case, would you run a telnet session
and log in as admin to a server across any of the three? Why or why not,
and what differences between the transmission technologies would affect
your decision?
 
Thanks in advance for any insights y'all might have. Also, references
to lists more specifically focused on these issues are appreciated.
 
Dan Lynch, CISSP
County of Placer
Auburn, CA