....this is the sudo password when you set the sudor for arpspoof. If you haven't set the sudor for it, you won't get thru no matter what.

You could just enter root to use that command, or you can set the sudor for this command.

Look at the directory under /etc/sudoers.d, take reference of other similar .sudoers and add you own, then run update-sudoers. Perform above as root, of course.