New Delhi, May 9 -- "Subject: Traffic Violation Notice. Immediate Action Required." This notification popped up on the phone of a 29-year-old librarian from Karampura in west Delhi last month. When she opened WhatsApp, a message awaited her. "Dear vehicle owner, we regret to inform you that a traffic violation has been recorded against your vehicle for violating traffic rules by jumping a red signal. Challan No. 123456, Amount due: Rs.5,000. To view evidence and resolve the matter, download your challan. Failure to do so may result in further legal consequence," the message read. Startled, she clicked on what seemed like a blurry photo - supposedly evidence of her red-light violation. But the file wasn't a photo at all. It was an APK - an A...