What is the ruling on a Muslim engineer working for a company that sells and installs computer networks for usurious banks, and is this considered cooperation in sin and transgression?

Means share the rulings of their ends, and whatever leads to the unlawful is likewise unlawful. It is forbidden to sell grapes to someone who will use them to make wine, because that constitutes aiding in the unlawful. Allah Almighty says: "And cooperate in righteousness and piety, but do not cooperate in sin and aggression." If network programs are sold and used for both permissible and impermissible purposes, there is no objection to that. However, if they are prepared for entities that engage in unlawful activities, such as usurious banks and commercial insurance companies, then it is not permissible to assist in their preparation, because that constitutes aiding in usury, and receiving payment for it is forbidden. The questioner must avoid directly performing these tasks and instead undertake other work within the company.