On a Wheezy box I saw this but was able to continue by answering yes to ignore the authentication warning.
WARNING: The following packages cannot be authenticated!
On a Stretch system, no can do. Apt was blocked from downloading updates.
W: The repository 'http://ftp.uk.debian.org/debian stretch/updates Release' does not have a Release file. N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use. N: See apt-secure(8) manpage for repository creation and user configuration details. E: The repository 'http://security.debian.org/debian-security stretch/updates Release' is no longer signed. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details.
First i thought someone forgot to update their repository keys.
$ sudo apt-key update
Nope. Still not downloading updates.
So I tried download the
Release file myself using wget – success. So then I tried to download the
Release.gpg file using wget – failed with an HTTP status code 500!
I could download all the files apart from the
.gpg file. I checked the corporate proxy for errors and sure enough the
.gpg files are being picked up by the Anti-Virus scanning. So a quick addition of a filter exception to disable the virus scanning for the Debian repository and my servers start updating again.