What controls the OS / distribution icon in the user info?
 

For interest ... there's an icon (with a text tooltip) in the bottom left of the user info panel of each post that seems to show the OS and sometimes distribution. How is this determined?

I've seen that mine is sometimes linux and sometimes linuxubuntu, but I've always signed in from the same browser on the same host.

It is set by your browser's user agent. No idea why it would change if you're always using the same browser.

Thanks, that makes sense. Do you know how often it gets updated?

My user agent is Mozilla/5.0 (X11; Linux x86_64; rv:7.0.1) Gecko/20100101 Firefox/7.0.1. Nothing in there says Ubuntu, to me ...

Hmm. I wonder if my user agent string changes.