A personal identification number (PIN number) is typically a numeric password/code that is used to access a personal account. A four digit PIN number is used be banks and financial instituations in connection to the debit and credit cards they issue to their customers. Debit and credit card PIN numbers are used at automated teller machines (ATM) and during point of sale purchase (POS). It is essential to the security of a customers bank account / credit card account that their PIN number is only known by themselves, or they risk their account being accessed by other people to defraud the account.
Automated teller machines (ATM) have been targeted by fraudsters to steal PIN numbers, fraudsters use a range of techniques to steal PIN numbers: the least sophisticated being 'shoulder surfing', and the more sophisticated being the use of magnetic card readers and surveillance cameras that are installed onto a ATM machine. Once a PIN number has been stolen, it is then possible for fraudsters to clone debit and credit cards. To combat the use of cloned cards, banks have introduced 'Chip and PIN' (EMV) smart cards that are more difficult to clone.
It is fairly common for people to write down their PIN number in a diary or organiser as a reminder -- especially if the person has multiple cards with a different PIN for each card. There are some security applications (anti-virus suites) with software that stores PIN numbers securely through the use of encryption -- while this option 'on the face of it' is the safest option for writing down a PIN number digitally, there is always the risk a hacker may crack the software due to the financial rewards on offer. Due to online banking there is becoming less need for anyone to have to write down a PIN number, while its true that a card will get locked if a PIN is entered incorrectly three times, it is possible to login (Barclays) to your bank account to receive a reminder for a PIN number.
The following steps should be taken to secure a PIN number from fraud -- most are simple common sense:
1) Most obvious of all: never write your PIN number down, or store it digitally; only place it to your memory.
2) Never tell your PIN number to anyone -- banks state not to tell your PIN to anyone; that includes police officers.
3) Do not allow businesses -- during point of sale purchase (POS) -- to walk away with your card; where you cannot see what they are doing with it.
4) Examine the ATM machine before using it; some ATM machines have devices installed by fraudsters to read and record your card number and PIN.
5) Watch for any suspicious individuals hovering over your shoulders when using a ATM machine. Use your hands as a shield when entering your PIN number into an ATM machine.
6) Shred all documents relating to your credit card which are not essential to keep; place statements etc, in a secure location.
7) Ignore "phishing" emails and telephone calls where someone asks for your PIN number; banks will never ask for your PIN number by email or by phone.
8) Use ATM machines within the bank where possible, rather than standalone ATM's.