Linux, being a unix-like OS, is unaffected by pc viruses. Of course,
nobody is claiming that linux is invincible, but it's a much harder
target for crackers. Linux users generally don't run any anti-virus
software and don't need to. Some shell shocked refugees from the
microsoft world sometimes insist on having anti-virus and a disk defrag
utility, neither of which have much use in the linux world.

The ubuntu website has some good user guides and the forum there is helpful.

It's very hard to write a "successful" virus for Linux because of the
built-in security features and as far as I know there has never been
an epidemic of viruses, trojans or worms in Ubuntu. It is possible for
the unwary to click on a link that invokes a javascript routine that
will do damage, but it's still much less lethal than in Windows where
every user has full run of the system files.

Most of the important system files in Ubuntu require root privileges
and only you know the password. I'm no expert and perhaps some of the
senior members can explain more fully.

Linux is a tiny target compared to windows and that is the other
reason that we are usually left alone by the bad guys.

No it doesn't suffer in the same way as Windows, says this is down the the way that system files are not accessible by
the user directly and also the need to give the system password to
make any changes at all to Ubuntu.

Not to say it can't be infected but the user needs to be tricked into
giving out that password when they shouldn't - so treat any request
that you get for this with suspicion if you are just web browsing or
opening e-mail. There is never any need for a web browser or e-mail
client to require root access... period <lol>

Nothing suffers virus and malware problems like Windows.

I have used Linux for ten years without using any antivirus protection and
have had an always on broadband connection and am a heavy user of the
internet. There are reasons to use AV protection, such as protecting friends
who use Windows by not passing on viruses, but because it is not a problem
with Linux, Linux AV applications are hard to set up and use. You need to
scan files manually or set up a cron job to scan your system at intervals.
They do not scan in the background because there is no need.

Malware also is not a problem. Linux is sandboxed. You user area might
become infected file by file, but the system can't be compromised, if you
follow Linux protocols and do not run as root. For this reason Ubuntu uses
sudo and prevents root login. There are a few rootkits that affect Linux but
if you follow protocol you are safe. You need to be stupid to provide
password access to enable yourself to get caught. If you are worried about
others doing this (children) then do not give them your password but set up
a user account for them without admin privileges (not members of sudoers
group). Keep yourself as the lone admin account.

There is some truth to the idea of Windows vulnerability and some good reason
for this as well. The first reason is (as mentioned on other posts) Windows
users have the (bad) habit of running with elevated privileges (administrator in
W and root in L). Take a look at a common issue in Microsoft security
bullitens:

"This security update resolves a privately reported vulnerability in MPEG-4
codec. The vulnerability could allow remote code execution ... An attacker who
successfully exploited this vulnerability could gain the same user rights as the
local user. Users whose accounts are configured to have fewer user rights on the
system could be less impacted than users who operate with administrative user
rights."

The Holy Grail of explotation is elevated privilege. Next Windows is a much
bigger target. Third is that Windows default tends to leave a lot of ports open
for numerous services widening what is called the threat surface. The more
applications available the more vulnerability. The common view of cyber threats
is that the OS is the primary target when in fact the Web Application is far
more vulnerable then the OS (and potentially more profitable). Currently there
are a lot of attacks by the Zeuss trojan on banks and this of course is profit
driven. The Stuxnet bug is presently attacking industrial systems by altering
PLC components. One of the most popular targets of hackers is presnetly hand
held devices such as cells. Linux is more resistant to attacks but not immune.
As the profit margin for Linux attacks go, there will be the scoundrel there
exploit it.