A Ranchi social worker lost hefty cash to cyber thugs after she made the cardinal mistake of divulging her debit card details to a fraud caller last year.

Reena Devi (35), a resident of Jada Tand in Kokar who runs a welfare group for women, lodged an FIR against unidentified people at Sadar police station on Wednesday, a week after she realised her SBI savings account had been raided nearly a month ago. She lost Rs 41,800 in instalments, the last withdrawal being on Tuesday.

Sadar OC inspector Bhola Prasad said a man who identified himself as SBI's Kokar branch manager Mohit asked Reena Devi to furnish her debit card details, including her ATM personal identification number or PIN. "When she hesitated, the caller told her that if she did not provide the aforesaid details, her account would be frozen. The woman fell into that trap," Prasad said.

Another officer said the social worker received the call from a mobile phone number, 9709695321, on December 16. "Small sums of money were withdrawn from 20 ATMs the same day, but the lady realised she had been swindled only when she went to the bank to update her passbook on December 29," the officer said.

Reena Devi had then lodged a complaint with the real branch manager who advised her to change her debit card PIN. "Before she could do that, more money vanished from her account on January 5 after which she approached police," the officer added.

Over the past few years, cyber crimes, including fraudulent financial transactions, have been catching capital residents unawares.

CID statistics show 43 cases in 2013. In 2014, the number was 120-plus. Last year, roughly over 100 cases were reported. If police insiders are to be believed, none has been cracked yet for want of expertise.