I'm currently using Windows XP and i'm planning to install Ubuntu. And about a couple of days, i was reading something on some forum, and i saw a thread called "Viruses for Linux computers". So i took a look. Some of them just said yes, some said no, some said the chances are very small, ... So now i don't know what to think. I want to install ubuntu just because n900 is running linux, so i want to become a little bit more familiar with the device. Please answer my question, and if it can get a virus, what antivirus software should i use and where can i get it?

I believe that you can but it is probably unlikely as someone with more knowledge could explain. From my understanding there are hardly any viruses that exploit linux in comparison with windows.

have a read of the wiki article.

http://en.wikipedia.org/wiki/Linux_malware
It does explain some of what you are asking.

Yes it can. However the chances are much slimmer than windows for many reasons. There is antivirus software, but I don't know any specific one...

IMO, antivirus is not needed on Linux, Windows, or Mac. Its more of a hassle than getting a virus...

I know someone who lives and works linux and has since it came into existence. He said linux has had something like 7 viruses since it was created. Of course those specific exploits have been fixed. Theoretically of course and can get viruses. But it's simply much harder to write them for it. And the linux community would jump on a weakness with speed (unlike Microshaft Winblows).

Note: I used to work for F-Secure but I haven't had really kept up-to-date with the malware scene since 2002.

First things first, there's more than one kind of malware and it's important to distinguish between them to understand the risks.

1. Viruses, these are self-replicating code that attach to executables (files, boot-sectors etc), the executable in question needs to be run in order for the virus to spread (however the virus might and probably will stay in memory even if the original executable exits) to other executables on the host machine.

2. Trojan horses. These are programs that on the surface appear to do something (usually something you would like, thus you are tricked into running them) but in the background (or simply instead of the purpoted function) they do something malicious. These do not self-replicate.

3. Worms, self-replicating code that actively seeks hosts to infect via networking. Worms can and often will use security holes to spread without any user interaction. Viruses that email infected executables (depending on the recipient to execute them) are not "full" worms IMO but often are classified as such.

I don't think you need to run any antivirus on your Linux (there are a few available, also F-Secure [though it's meant to protect files on servers that windows machines have write access to...]).

That does not mean you can mindlessly execute just any executable someone mails you (or you download from the shady corners of the net), especially not as root (or via sudo). Also trying the funny looking bash oneliners sometimes posted on certain forums is not neccessarily a good idea (these could be classified as trojans)

In short: The risks are much smaller but it's not excuse to behave irresponsibly.

Then to "does linux have viruses" part, answer is yes, also worms and trojans. I don't think there are any Linux viruses or worms in the wild at the moment, I recall a few years back a worm exploiting bug in some php based board software to "infect" linux servers but this only means to the end of infecting windows machines through a famously vulnerable browser...

Trojans, also don't recall that there are any in the wild (if you don't consider the bash oneliners that fork-bomb your machine to it's knees [reboot solves this, but linux users are less tolerant of constant reboots...] trojans).

As for windows; it's possible to survive without antivirus but you really need to know what you are doing then (these days virus/worm writers are more oriented to making a profit in some way then just annoying you for the lulz)

It is really difficult to get Linux infected as long as you are using only the default user account or a custom created account without root permissions. But if you use the "root" account all the time and set the permissions wrong then -> yes.

At least on a PC it is for example dumb to give a webserver account root rights, that way someone may could abuse a exploit and get root access to your machine. Its similar with your phone, a "bad app" could harm your phone when it gets root access which is only possible when you allow it.

Still as long as you install only applications from the default Noka / Maemo repository's nothing should happen to your Maemo based phone.

However it only needs your user privileges to royally ruin your day in multitude of ways. Lets not get stuck with the separate root vs user privileges mindset. While the privilege separation makes many things harder for malware it will not solve the problem.

Something that might be better than a Anti-Virus is the community. As there are many "nerds" running linux a virus will have a hard time replicating it self without notice. There is also many flavors of linux so it must attack core functions. So you might get a virus but it will not get spread to someone els.

I have Avast running sometimes mostly in case i need to send something to a friend with Windows. There is AVG and Clamp too.

In practical terms, you'll run a higher risk than the generally VERY low risk of a malware infestation if you stray beyond the official and community repos or start doing silly things with the inherent security defaults 'to make life a bit easier' or some such.

BTW, as an alternative to Ubuntu, consider SimplyMepis or Linux Mint. Have a look at distrowatch.com.