You may want to read this answer here on a similar thread:
The HUD is related to the Unity Launcher. For example it analyzes the
files you are using and offers them when you press Super.
On my system (Ubuntu 15.10) the hud-service started using 100% of one
I solved this by installing Compiz Config Settings Manager (ccsm) and
disabled all effects and set "Enable Low Graphics Mode" in "Ubuntu
sudo apt-get install compizconfig-settings-manager
Although you can indeed disable the executable bit, when the system upgrades, it may reset that bit to on when the file is overridden on new updates.
Also, the comment above the one I posted above mentions that the hud-service is in the package
hud, which if you just don't want, it might be better to just remove the package entirely.