Kernel updates & security patches

[Jeff Penn <jeff@jrpenn.demon.co.uk>]

I'm running a dialup workstation using Sarge with 2.4.18 compiled from 
a source package.  I'd like to understand the Debian approach for 
keeping the kernel up to date (preferably using a minimum of 
bandwidth).  

Do package Debian kernel patches?, or are they only available for the 
gerneric Linux kernel?.  Are there any limitations to applying patches 
(2.4 -> 2.6) or can only minor versions be patched (2.4.18 -> 
2.4.19)?.  

Does the Debian security mailing list announce kernel related security 
alerts, or should this be monitored through services such as bugtrac?. 

thanks
Jeff