They reiterated a message for people to be vigilant against fraudsters using telephone and computer scams to divert money from bank accounts.Chief Inspector Tony Callaghan, the Area Commander, said that some of the frauds had involved quite significant sums of money."We believe that a gang of criminals is behind the incidents and is exploiting a lack of knowledge by the customers of banks and other financial institutions," he said."The themes of the approaches vary, but they are generally aimed at getting people to disclose personal financial details such as PIN codes."In many cases the callers say they are from certain banks or other financial institutions. A typical ploy is to claim that a suspicious transaction had been identified in a person's bank account and that often leads on to persuading the individual to transfer money from a genuine account into an another account, which, of course, the fraudster controls."Ch Insp Callaghan advised anyone approached by phone or email not to give out their financial details or agree to any transaction and to check the legitimacy of the query by contacting the named bank on a genuine number."It has been known for fraudsters to keep the telephone line open after their conversation so that when you make a call, you are talking to them again," Ch Insp Callaghan added."Avoid this by first of all making a call to a family member or friend so that you can be sure the line is clear."Many banks also offer 24-hour customer services telephone support. You should take the number from official bank statements."The officer stressed that fraudsters used a number of different scenarios and that all calls should be treated with a degree of caution until they had been checked out.