And even that isn't needed.

by R. Proffitt Moderator - 2/21/13 4:34 PM

In Reply to: Modify cable modem to capture data flow? by deadringer

http://www.securityfocus.com/news/353

"According to Hallacy, a savvy network programmer could change his configuration file to intercept all data from other users on the attacker's local area or "node"."

I noticed that issue in the 90's as I could see other folk's PCs and printers on cable back then. So the issue is not just your cable modem. Luckily most folk install a router after the cable modem which helps a lot.
Bob