"Look at this big ol' Ubuntu security resource as an
introductory guide to securing Ubuntu, along with a list of the
software you'll need to stay protected.
"Surprisingly, many new Ubuntu users fail to take the most basic
steps toward securing their install, even when they know better.
Thankfully, the list of critical changes isn't long. Making
modifications may not excite you as much as, say, adding a whole
new security program, but these simple changes will go a long way
to closing up Ubuntu's security weaknesses."