Vishing works in much the same way as phishing. An email or text message is sent to a user asking them to call the target bank to reactivate a credit or debit card.
"On calling the telephone number, the recipient is greeted with 'Welcome to the bank of ...' and [is] requested to enter their card number in order to resolve a 'pending security issue'," the FBI's
Internet Crime Complaint Center said in an alert.
The availability of increasingly popular VoIP equipment and open source call-centre software has prompted scammers to set up their own call centres, often employing staff who may be unaware that they are working for a criminal gang.
The FBI is advising users to look up their bank's phone number and call them directly if they believe they have been a victim of a vishing attack.