What is the ruling on working for a company that installs information systems for institutions that conduct usurious transactions with banks?

It is not permissible to create information systems for companies and institutions based on unlawful activities, such as usurious (interest-based) and commercial insurance, because that entails cooperation in sin. As for companies whose primary activity is permissible, there is no harm in installing information systems for them, even if they occasionally deal with usurious banks. The impermissibility lies in dedicating the service to unlawful purposes. The determining factor is the predominant activity of the company, otherwise people would fall into great difficulty.