There's safety in numbers

Try not to use a security code or PIN that could easily be guessed by a fraudster, for example your date of birth.
Do not disclose your security code, Secure Personal Information or PIN number in response to unsolicited emails or telephone calls claiming to be from your bank or the police
The Co-operative Bank will only ever ask you for two digits of your security code over the telephone or when logging into the Internet Banking Service.
Never write down your password, Internet login details or PIN number.
Change your security information immediately if you suspect that anyone else may have gained access to them