[ubuntu-in] Intrusion detection tools

[ramnarayan.k at gmail.com]

Hi

While accessing the internet via dial up i use win xp and Norton NAV2007
as my os and antivirus to connect to the net. The NAV2007 shows up a
fair deal of intrusion attempts - from a series of similar looking ips
61.x.x.x.

NAV2007 throughs up a pop up saying intrusion detected.

My question is on Ubuntu - how does one figure when attacks of any
nefarious kind take place. Funnily enough while on dial up i have not
been able to use linux - on braod band (adsl) or using reliance i only
use Ubuntu - am assuming that a better connection means more attacks and
stuff so how does one
a. Keep track of whats happening (attacks, intrusions etc)
b. prevent such stuff.

appreciate your advice

ram