[vagab0nd]

For linux users you can "turn off" internet for a single program: https://news.ycombinator.com/item?id=21146655

[rkeene2]

I actually wrote an even better way to do this, since my build system drops network access after downloading SHA-256 validated source (to ensure that source can't go out and fetch more things during build):

https://chiselapp.com/user/rkeene/repository/bash-drop-netwo...