if I understand the question, you want the router attached directly to
the cable modem. the first level of security is provided by the
router. the router protects the computers, not the other way around.
consider establishing a computer station in the shop and running
ethernet cable to it.
this might help (or not)
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.