A 4-digit PIN allows for 10,000 possible combinations, from 0000 to 9999. This means a thief trying to guess your PIN has only a 1 in 10,000 chance. Plus, modern banks block the card after three wrong entries, stopping any ‘brute-force’ guessing attacks. So, four digits are seen as the perfect balance between security and convenience. What’s the scene today? With technology advancing, some international banks have made 6-digit PINs mandatory for extra security. However, the 4-digit system, born from Caroline’s simple suggestion, still rules the ATM world in most countries.
