Updates
From time to time, software companies and independent programers release new
and improved versions to their software; these are known as updates. Updates
usually install new features or fix problems. Usually, you should download
the latest updates to improve system performance though it’s sometimes wise
to wait a little while to be sure the update itself does not cause problems.
Many programs update themselves and this process is know as an automatic
update. If you have to manually update your software, do so through the
software developer’s site, not through a secondary source. This approach will
reduce the chance of contracting a virus or other piece of malicious software.

Windows
A newly installed Windows XP computer using a broadband connection can be
attacked within moments of being connected to the Internet. In severe cases,
the attacks can render a system unbootable or make a second reinstallation
faster or easier than manually removing the malicious programs causing the
problems. The SANS Institute provides a PDF guide called Windows XP:
Surviving the First Day, which explains how to update a new Windows XP box
without immediately becoming infected by viruses and worms. To avoid having
your new computer attacked, install a firewall, or activate the one that came
with your OS. Both Windows and GNU/Linux have in-built firewalls: In some
GNU/Linux distributions, it is enabled by default; in Windows XP Service Pack
2, it can be found by going to the Start button and choosing “Control Panel”
then double-clicking the “WIndows Firewall” icon.
As soon as you are on the Internet, run your operating system’s update facility
to fix any security flaws that have been found since your CD was printed.
To do this under Windows, simply click on your Start Menu, click on ’All Programs’,
and then click on Windows Update, and follow the instructions. If you
use other Microsoft products, such as Microsoft Office, then it can be valuable
to use Microsoft Update, which covers updates for all Microsoft products. For
either of these, you can also switch on “Automatic Updates” from the Security
Center program mentioned above.

GNU/Linux
The method of updating your GNU/Linux system varies greatly from distribution
to distribution.
For SuSE, there are two ways:
1. YaST
2. ZENworks updater
For Fedora, type
yum update as the root user inside a terminal window.
It is perhaps easiest to update the OS from Debian-based distributions such
as Debian, Ubuntu and Linspire. For Debian and Linspire you type the following
into a terminal window while running as the root user:
apt-get update
apt-get dist-upgrade
Ubuntu has you run sudo to switch run a program as root. Type the following
into a terminal:
sudo apt-get update
sudo apt-get dist-upgrade
Automatic updates
If your computer will be running overnight, it may be good to have your computer
update itself.
Debian based      cron-apt
Windows               Windows Update