/usr/lib/x86_64-linux-gnu/libnux-4.0.so is in libnux-4.0-dev 4.0.6+14.04.20140409-0ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libnux-4.0.so.0.6.0
/usr/lib/x86_64-linux-gnu/libnux-4.0.so.0.6.0