Answered by Sayyidi Habib Umar bin Hafiz (may Allah protect him and benefit us by him).
What is the ruling on working in a bank which deals with interest?
If the bank conducts other financial dealings in which there is no interest then it is dubious to work there. If it only deals with interest then it is forbidden to work there. Working in such an institution constitutes recording and assisting transactions in which there is interest.
 The Prophet ﷺ cursed the two parties involved in usurious transactions, as well as the one who records those transactions, and the two people who witness them. (Narrated by Muslim, Abu Daud and al-Tirmidhi)