Nagpur: A gang of advanced hackers, with its mastermind in China, is operating an app-based sextortion racket on the pretext of offering instant loans. After pocketing more than Rs50 lakh by threatening over 500 victims in last few months, two of the gang’s operatives — Kaif Ibrahim Sayyed (25) and Irshad Ismail Shaikh (32) — were picked up from Karad in Satara by a team of Ajni police station under zonal deputy police commissioner (DCP) Noorul Hasan on July 25. Cops are learnt to have zeroed in on the accused duo with the help of mobile phone technology and other…