How to hide outgoing url's this way

Hello,

There are several plugins which let you turn around your outbound url’s using url shorteners.

I am looking for a way that it automatically changes all url’s going out to https://www.mysite.com/out/1 (or a random number)

For example:

https://www.externalsite.com/afadkf.html

will become

https://www.mysite.com/out/1

Do you have any idea how this can be done?
Thanks