As the saying goes, viruses on Linux are hard to get right because you need to make assumptions about API/ABIs, libraries, required dependencies, etc. which is never assured across-the-board.
Oh wait... Good desktop software needs all that too...
Oh wait... Good desktop software needs all that too...
The problem is that the word “virus” is not of any technical significance. The way I see it there are two important classes of malicious software:
1) The class that relies on being executed normally by the user, but then does things contrary to what the user expected it to.
2) The class that actually exploits design oversights to be able to run with privileges, or run at all, when it was not intended to by the user.
The latter class is obviously of a significantly larger concern.
“GNU/Linux” is also a social buzzword bereft of any technical meaning. Nothing exists that deserves to be so grouped together under “GNU/Linux” for any technical reasons, and the exploitations that class 2 exploits often have nothing to do with it.
There recently was such an exploit that allowed malicious code to be executed ex nihilō. More specifically, it relied on an indexing dæmon that ran in the background and indexed media files, by creating a specifically crafted malformed image file, it could trick this dæmon into executing arbitrary code, apparently even as root as the dæmon ran as root and was shared between all users as I read it.
Such exploits are not a “GNU/Linux” issue; they are an issue of whatever system has this dæmon both installed and running. Apparently Fedora had, but my system does not.
The majority of such escalations these days seem to have little to do with either GNU or Linux, and mostly seemed to exploit “Freedesktop”, which is known to favor copying certain design sensibilities from Windows and with it the kind of escalative holes that such design sensibilities often bring with them, such as the aforementioned.
The Linux system call interface is stable. Or if you want to go up one level of abstraction, glibc has great backwards compatibility (using versioned symbols).
GNU/Linux viruses are fairly uncommon, because (virtually) no one uses Linux on the desktop. So, it is much harder to spread.
(Disclaimer: not a bashing attempt, I use Linux on the desktop.)
As long as the virus or other software dev can restrain themselves from using the latest added features to glibc and c++??. Usually they can't so compiling something written with today's libs on a distro from 5 years is infeasible.
Maybe you are thinking at those terrible web based viruses where an Windows XP themed popup appears that tells you that you need to download and run something to fix your computer. So it is harder for those guys to detect the correct theme to use for their popup to trick the user.
Are you saying it's not possible to have good desktop software on Linux? Users of JetBrains' IntelliJ IDEA and users of, say, Blender, are going to disagree (for example).