"a piece of code which is capable of copying itself and typically has a detrimental effect, such as corrupting the system or destroying data."
MS pushed Windows 10 onto my Windows 7 machine.
Had a detrimental effect in corrupting my system such that some of my drivers for legacy (yes go out and buy new shiny shiny toys, I know) peripherals no longer worked.
Destroyed data in that my XP Mode VM and all it's contents and applications was suddenly wiped, couldn't find it anywhere, and the built in executables sol.exe and winmine.exe were long gone, to be replaced by ad driven freemium 'adventure' games.
(If I wanted to play freemium games I'd load my mobile full of crap like candy crush, which seemed to be installed, unwantedly, by windows 10)
Also added unwanted Adware to my start menu, what was previously an operating system control for launching applications was now telling me to go buy an Xbox or to subscribe to the weather channel, alerts telling me to buy subscriptions to Office and Skype premium. Urging me to use their Cortina spyware, and "BING!!" search engine.
I was half expecting the Bonzi Buddy to pop up.