Is it possible for virus in windows to infect ubuntu?

Solution 1:

I have to agree with MDT Guy, it is highly improbable. I'll also assume that you use the term virus - as most people - for malware in general and not a particular malware category.

• Linux and Windows have different executable file formats (ELF vs. PE is the most usual case) - at least for binary executables
• Most wide-spread malware these days has a "commercial" background, i.e. the authors try to gain financially from infecting your machine, be it through:
  • fraud (e.g. skimming bank data or modifying transactions)
  • selling your machine's computing power or bandwidth as one of many botnet drones
  • direct extortion, i.e. ransomware
  • there are plenty more schemes out there (check the Wikipedia article here) ...
• Even if the malware was scripted, malware authors aren't exactly known to be too concerned about stability or compatibility (with a few notable exceptions) of their concoctions (best shown with frequently crashing Windows KM rootkits). So scripts would be one possibility for cross-platform malware. I'm not aware of anything beyond jokes.
• Extending on the previous point, Javascript worms exist and so do rogue addins/extensions - and if you configured your favorite browser to share the profile from Windows with the Linux machine, it is possible to carry this over. Note: this won't affect plugins, as these are binary executables (see first point).
• Bootkits would be another possible case for cross-platform malware. I haven't seem anything beyond concepts there, however. And it would be rather hard to get right given the diversity of kernel configurations on Linux.
• UEFI malware and older variations on this theme are yet another possibility.

So again, highly improbable but not entirely impossible. You know best whether you share your browser profiles across those platforms.

One more thing. Many Linux (also MacOSX) users fall prey to the assumption that malware that doesn't have privileged access can't hurt you (which is also often cited as a reason why there "isn't" malware for unixoid systems, which also isn't entirely true). This couldn't be further from the truth. Although this prevents it from establishing a system-wide stronghold, it won't keep malware from skimming data from your personal files etc. A rogue browser extension installed in your own profile will still be as dangerous to your account as the one that can do it to all accounts. If you do your internet banking with the rogue extension installed, it makes no difference whether you are root or joe.

Partial disclosure: I work for an AV company, but won't tell which :) ... but keep in mind: Strictly speaking we can never tell whether a system is clean, whereas we can state that we didn't find anything. Every claim to the contrary is either Marketingese or is going to obsolete the AV industry as a whole quickly.

Solution 2:

No. This is HIGHLY improbable if not impossible. Code from one OS won't run on the other and vice versa.

Solution 3:

It's not likely*. Executable files for Windows exist in a specific file format that other non-Microsoft OSes are unlikely to be able to run without emulation. (Such as WINE.)

The idea is that a virus would also be written in an OS-specific format since a computer virus is merely some executable code that does something bad/without permission, and only run on an OS that can execute that format.

There's a chart, here which compares the features of several formats. You can mouse over them and/or click through them to see which OSes run them.

*Which means someone's probably done it, it just didn't catch on/wasn't practical/we just don't know about it/I just don't know about it, etc.

Back when I worked in technical support the policy for infected customers was to recommend flattening the machine and reinstalling from scratch. With two major OS types installed you're probably ok, but I'm not qualified to speak to "Oh maybe your boot sector is infected and will just reinfect the next instance Windows you install" - I really don't know anymore.