According to comments on the internet, I'm not the only one to whom this has occurred, and I must say that I'm rather upset about it. I have been running the Avast! free antivirus program for quite a few years, and have been almost universally happy with it. It has caught all but one virus / malicious http connection in that time, and thanks to a contest of theirs, I even had three free one-year Pro subscriptions for my computer. I was therefore disturbed to notice that after Avast! prompted me to install version 7, I had Chrome installed, pinned to my taskbar, and set as my default browser. Assuming I had just missed the opt-out checkboxes, those invasive scum of modern freeware/shareware, I went through the upgrade process on my desktop too, and lo and behold, not a single warning or option to opt-out of the Chrome install. Have you run into this same problem? I am hesitant to switch away from Avast!, considering how dependable it has been, but I am also loathe to stick with a piece of software that installs other software without asking.

Oh, wow, it does that? That's rather shameful. I can't say if the same happened to me as I am a Chrome user so I would not have seen a difference.

Maybe it was just a mistake on the avast! team's part, something they forgot to add or something. //benefit of the doubt

edit: according to some google searches, apparently the check box is there, but the window showing the check box disappears too quickly for you to uncheck it.

I read those topics as well, but when I double-checked the install process on my desktop, I'm positive that no option whatsoever appeared.

When I updated on my laptop it did not happen, but strangely when I updated my desktop it installed it. I do believe that there is an opt out option though.

Don't run Windows or OS X. Problem solved.

Safe for now, although I wonder how long it will be until malware writers start targeting some of the more widely-used Linux distributions like Ubuntu, trying to sneak something into one of the obscure packages.

SELinux. Problem solved.

What? How does that solve the problem of viruses exploiting bugs in Linux?

If you put the settings of your user account correctly, you can have antivirus-like control of your computer. (Of course, it still doesn't help if you do something as root, but it adds another layer of security). Problem contained.