For some days I got the red circle in the notification bar. After not being able to run software-updater, I tried using apt-get update.
This is what I got:
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://dl.google.com stable Release: The following signatures were invalid: BADSIG A040830F7FAC5991 Google, Inc. Linux Package Signing Key <firstname.lastname@example.org> W: Failed to fetch http://dl.google.com/linux/chrome/deb/dists/stable/Release W: Some index files failed to download. They have been ignored, or old ones used instead.