University IT (UIT) maintains mirrors of the main Debian and Ubuntu package repositories here at Stanford. These repositories are stored on a server with a large NFS volume. We update the mirror three times per day, or every eight hours.
Here are the endpoints:
http://debian.stanford.edu/debian-security/ (deprecated; see note below)
We mirror the current stable, the previous stable, as well as experimental, sid, and testing distributions. We have deprecated the "http://debian.stanford.edu/debian-security/" endpoint; for security updates use instead "http://security.debian.org/debian-security".
For more on how Debian repositories work, see Debian Repository Format.
We also mirror several Ubuntu distributions, including the current LTS (Long Term Support) distribution.