Failed to fetch http://security.ubuntu.com

27 Aug 2014 W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/quantal-security/main/binary-amd64/Packages  404  Not Found [IP: 91.189.91.14 80]

This is happening because you're on an unsupported/old version of Ubuntu.

One way to fix it:

1. nano /etc/apt/sources.list
2. Change all entries referring to http://archive.ubuntu.com/ubuntu to http://old-releases.ubuntu.com/ubuntu