Will malware in Windows affect Ubuntu in other partition?

Question

If I run Ubuntu and Windows on a single machine in separate partitions, will viruses and other bad migrate between the two operating systems? In other words, will bad stuff under one OS infect the other?

Answer 1

Could malware feasibly go from one install to another?

To be clear, the malware running on one probably won't run on the other as is... But most malware is more than capable of downloading other malware. That's what most do —by design— to stay alive these days.

And if you can access the other partition, anything else running on your computer can.

So any malware in Windows could detect an Ubuntu install, download Ubuntu-specific malware and drop that on the Ubuntu partition.

Have I ever heard of anything doing this?

No... But I haven't heard of a lot of things.

If you're doing dodgy things in Windows (or Ubuntu) and you don't want that to affect anything else, seal it off from the world. Wrap it up in some proper virtualisation (eg VirtualBox) and disable any sort of sharing with the rest of the system.

If you're just worried about what Windows is doing, just follow the best possible security practices (don't browse dodgy sites, don't download cracked games and applications and use a self-updating browser that isn't IE) and you will probably be fine...

... Probably. There really are no certainties. Even with Ubuntu.

Answer 2

It is possible, but I am unaware of any common examples, the probability is low.

If the malware is programmed to recognize other operating systems and write data into the partitions where those OS reside - they could easily look through mounted drives (local or network) search for various executables and inject their code.
But Windows is generally not very good at writing to Linux filesystems, which requires the loading of 3rd party drivers, its going to make the malware bulky and easy to detect (or a lot of effort to obfuscate).

Considering the low number of malware that target Linux specifically (compared to other OS like Mac/Windows), dual booting is even less popular and not worth the effort.