What is the ruling on working in the information technology department of a bank that deals with both usury and Islamic transactions simultaneously?

If your work at the bank is specifically related to permissible transactions that comply with Islamic law, and has no connection to interest-based (riba) transactions, then there is no harm in it. However, if your work involves all of the bank's activities, including both permissible and prohibited transactions, then it is not permissible for you to work there. This is because it would be considered assisting in usury, and Allah the Almighty says: "And do not cooperate in sin and aggression. And fear Allah; indeed, Allah is severe in penalty."