Everything on a Chromebook or Chromebox is accessed by using a url. To prevent users from accessing crosh by either typing in the url or by using the shortcut keys (pressing ‘CTRL+ALT+T’) follow these steps.
Press CTRL+ALT+T to open crosh, look at the URL and copy the part after chrome-extension://
nkoccljplnhpfnfiajclkommnmllphnl/html/crosh.html
Next open your Google domain management console and go to "Device Management > Chrome Management > User Settings".
Open the desired organisation unit (Tip: this could be at the domain root and you could just remove the setting from being inherited in your admins org unit/group). Then look down the page for the policy setting called "URL Blocking".
Paste or enter into the box "URL Blacklist box" the url address copied from earlier.
"nkoccljplnhpfnfiajclkommnmllphnl/html/crosh.html"
To test it, go to on any Chrome device and type in the url "chrome://policy", then click "Reload policies".
Now when you or a user tries to open a crosh terminal tab a message will be displayed saying "Webpage Blocked". This policy change will take a minimum of 30 minutes to apply to the rest of your Chrome devices (dependant on what's set in your Google management console).