By Elizabeth Dilts Marshall WASHINGTON (Reuters) – U.S. banks are preparing for retaliatory cyber attacks after Western nations slapped a raft of stringent sanctions on Russia for invading Ukraine https://www.reuters.com/world/india/war-with-ukraine-putin-puts-nuclear-deterrence-forces-alert-2022-02-27, cyber experts and executives said. Tensions between Russia and the West escalated on Saturday as the United States and its allies moved to block https://www.reuters.com/world/europe/eu-announces-new-russia-sanctions-with-us-others-including-swift-2022-02-26 some Russian banks from the SWIFT int…