KOLKATA: A group of five engineering students has robbed a bank of crores by using fake mobile wallet transactions over the last four months. Though all of them, along with four others, have landed in police net, the cops are worried over the alarming trend of youngsters exploiting tech loopholes to dupe customers and banks alike.A private sector bank, which had opened its wallet transaction operations in December, did not realize that there was a basic flaw in their system. If a customer tried to pay from his own wallet to another wallet holder — and the latter knowingly or unknowingly had his internet connection switched off — the one who is tranferring the amount did not end up losing any money. Instead, it was the bank that ended up paying for him. The bank did not realize the fraud till Rs 8.6 crore was siphoned off.The bank fraud section of the detective department has so far arrested nine persons. Jewel Rana, the gang leader, is one among the five students.Apart from the age and profile of the accused, the investigators are particularly alarmed over the fact that the gang was supplied with thousands of pre-activated SIM cards in the border district of Murshidabad to carry out the daring operation. Innocent villagers were asked to open accounts and wallets with this bank using these SIM cards. A cash incentive was promised for those registering for the scheme."Jewel was known to Habibur Rehman, a dealer of a mobile service provider in Murshidabad. While Jewel was the brain of the gang with the college students arranging the wallet transactions, the unnaccounted and unverified SIM cards were all arranged by Habibur's men," said joint CP (crime) Debashish Boral.According to police, it was on December 23 that senior bank officials from the Kolkata office lodged a complaint with Lalbazar that someone was withdrawing money from their accounts by using thousands of their newly launched mobile wallet service. A probe found that the accused had managed to open around 2000 accounts across Kolkata and Murshidabad with the bank. Against these accounts, over 18,000 wallets were created."We are investigating the case but it may take us some more time to dig into the details. It seems the accused used fake wallets to carry out a cheating operation of unprecedented magnitude. The arrests were carried out from Kolkata and Hariharpara in Murshidabad. The gang operated from Hariharpara," said an investigating officer.The detective department is working in tandem with the bank's investigating team. "The procurement of the SIM cards by violating all TRAI regulations will call for a separate probe," explained a sleuth."Wallets are proving a major headche for cops at Lalbazar. We have come across a few wallet apps that don't follow basic rules, like encrypting the data when a transaction is taking place," said a senior officer, citing the example of tech blogger and e-marketing consultant Sidharth Bhansali. He lost money kept in his wallet because of a security glitch. A fraudster accessed his wallet and operated from it. Bhansali saved screenshots of the transactions and took the matter up with the wallet company. After months of legal battle, the wallet company apologised and offered compensation. "Unless the wallet is security-proof, there are crooks ready to pounce on the opportunity," he said.