Yes Bank has tightened security measures after detecting unusual transaction declines on its Multi-Currency Prepaid Forex Card issued with BookMyForex. Fraudulent attempts occurred at 15 Latin American merchants where two-factor authentication is not mandatory. Transactions worth $0.28 million were approved for 5,000 customers, while 688 unauthorised attempts were blocked. The bank has restricted certain overseas e-commerce transactions and is initiating chargebacks to prevent customer losses.