/usr/lib/x86_64-linux-gnu/libasyncns.so is in libasyncns-dev 0.8-5build1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libasyncns.so.0.3.1
/usr/lib/x86_64-linux-gnu/libasyncns.so.0.3.1