/usr/lib/x86_64-linux-gnu/libnux-4.0.so.0 is in libnux-4.0-0 4.0.8+16.04.20160209-0ubuntu2.
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.0.8.0
/usr/lib/x86_64-linux-gnu/libnux-4.0.so.0.8.0