Why aren't viruses an issue? [duplicate]

In no modern Operating System viruses are an issue for the sensible user. So viruses are an issue if you're not sensible.

Viruses in fact don't get harmful unless you actually run them. That's almost the same in every different O.S., and do mistrust people telling you "Linux is good because Windows has got viruses" because it's nonsense. Linux (and Ubuntu) is good for many reasons, but this has nothing to do with viruses.

However, running Ubuntu or Linux in general lets you be statistically less prone to get infected by viruses. Ubuntu encourages users to choose official repositories as the main source of software (which are safe), and running an executable by double-click is less easy than in Windows.

But you can still get into a website that asks you to add a poisoning repository, or to install a malicious .deb (with double-click) to add some awesome functionality Ubuntu is missing.

So viruses are a problem because of the user, not because of the system (which in most cases is an innocent victim), even if in some old Windows systems (95, 98, ME but also old versions of XP) one could get a virus without doing anything unsafe, just through some vulnerability of the system. But leaving out pointless chat topics (Micro$oft is baaad, etc...) nowadays Windows systems are safe enough for the use cases they're intended and do get infected because of user inexperience and IT unknowing.

So, to answer your question:

1. Windows users are usually less competent users and get infected with ease
2. Ubuntu users use repositories which are safe

In no way Ubuntu is stronger towards viruses, I can write one tomorrow, pack it in a .deb, and it would be insidious and destructive also because people think "linux has no viruses". Linux has no viruses until you create one, which can be done in minutes, assuming you can convince the victim that it is safe to execute it.

Speaking of all the security issues in general, but leaving out the viruses, Ubuntu has build-in security.

However, Ubuntu will not stop you from installing malware like the Windows anti-viruses try to do. For example, if someone tricks you into installing software that will spy, spam, or destroy all your data then you're out of luck.

Many more security mechanisms are available if you choose to set them up: firewall rules, anti-virus scanners, network monitoring, two-factor authentication, etc... These additional mechanisms are mostly intended for servers and you should not need to worry about them as a desktop user.

Having that said, there are many vulnerabilities and Linux systems get broken into every day all over the world. Security teams come-out with updates to fix these vulnerabilities regularly. Ubuntu has it's own security team that releases updates and advices for systems administrators.

Here is an overview about anti-Viruses and Ubuntu security.

In practice Ubuntu is much safer than Windows. In terms of exposure to malware, Ubuntu is comparable to Mac. But as @Giacomo pointed out, living in a nearly virus free world can leave Mac users naive.

The top 2 things that you can do to stay extra safe:

1. Install software only from the official repository
2. Keep your software up by letting the Update Manager do it's thing

There do exist "viruses" for Linux. Or rather, software that runs on your Linux computer without your consent (presumably for a malicious purpose). An example is a script disguised to look like a common command which serves as an IRC spam bot (this happened to a friend of mine -- the attacker gained access via SSH by guessing a user's password due to my friend's carelessness).

With that said, to actually get a virus on Linux is difficult. What I mean by that is that a typical user will most probably only ever get a virus if he or she executes a malicious script (don't run scripts you're not familiar with) or sets weak passwords that are easily cracked via SSH or otherwise. This is because a user in Ubuntu has limited privileges.

The best way to combat viruses and attacks (like the above-mentioned SSH attack) is to implement some basic security measures like restricting SSH access to your machine to certain domains (or not having SSH run at all), choosing a good password, and being careful.