A top investigator into the electronic theft of $81 million from the Bangladesh central bank is turning his attention to some IT technicians from the bank whom he suspects hooked up its transactions system to the public Internet, giving hackers access. In a series of interviews this month, Mohammad Shah Alam, a Bangladesh police deputy inspector general who is heading investigations in Dhaka, went into some detail about how insiders at Bangladesh Bank may have helped in the execution of one of the world’s biggest cyber-heists last February.