Unauthenticated update

I installed some time ago Mint 10 on an old desktop, for a friend. It hasn’t been updated for a while and when I tried it, there was a warning:
“You are about to install software that cannot be authenticated!- and then followed a long list.
There were also many OK packages.

I would be very grateful for advice on how to proceed.

Mint 10 was based on Ubuntu 10.10 … that version is “end of life” and the repos have been archived, so it will receive NO updates (and any that were previously queued will not be able to be authenticated).

Really you should move to a more recent version as that will likely still be open to things like the heartbleed and bash vulnerabilities.

Thank you Mark - that is what I shall do. I didn’t think of checking the end-of-life.