I'm trying out Ubuntu. Been a Mac user. I like ubuntu a lot but I find it unnerving to not have any control over what apps can & cannot connect to the internet. I was advised that "ld_preload" can be set so that I can permit firefox traffic over port 80 but prevent Dash from connecting to port 80.

Can someone explain how I can accomplish this with ld_preload?


1 Answer 1


Perhaps a better option is to use ufw to disable outbound traffic, and only enable it for specific ports. That is not application specific.

I think to really get application specific, you need to start messing around with AppArmor. I am not quite sure, actually limiting per-application is a difficult problem.

For example, system-wide installed Firefox might be allowed outbound connections, but what about a copy of Firefox in your home folder?

  • Yes, this is the problem. There appears no way to control app's internet connections. AppArmor is very difficult to use. It requires advanced knowledge. So I am looking for app that has a GUI to make it more usable. This question arose from here: askubuntu.com/questions/135135/…
    – Lindsey
    May 10, 2012 at 20:00
  • 1
    BTW LD_PRELOAD is normally used to perform interpositioning of code between your application and system libraries, or to use alternate libraries, or locate libraries not in common paths between running. So it could be used to deny Internet to apps, but I think it's a little clunky also (not exactly designed for it). And probably simplistic to circumvent by an attacker.
    – theonewolf
    May 10, 2012 at 20:09

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