Since all protection in cars (no matter how complex is) is mass produced, it is very easy for thieves to purchase same/similar car and study it. However, I'm wo

Since all protection in cars (no matter how complex is) is mass produced, it is very easy for thieves to purchase same/similar car and study it. However, I'm wondering what will happen if an ordinary Hacker Joe (a guy who knows a little bit of electronics and software) installs custom protection, no matter how simple is? Knowing that for thieves, the most precious resource is time and if you force them to work more than expected, they might gave up...