Is it permissible to work on installing computer networks for a company that produces alcohol, knowing that the network will be used to market its products, and is it permissible to provide technical assistance to those who do this work?

It is not permissible to assist a company whose primary products are forbidden beverages by installing networks or other means, due to the generality of Allah’s statement: "And cooperate in righteousness and piety, but do not cooperate in sin and aggression." The fact that the installer is not Muslim does not make it permissible to provide information, as this is considered cooperation in sin and aggression.