Zero Day by Zaidi, S. Hussain

Mumbai is in a state of chaos. All the traffic signals across the city have stopped working. Shahwaz Ali Mirza, head of the Maharashtra Anti-Terrorism Squad, receives an anonymous email that claims it was a Distributed Denial of Service (DDoS) attack by the sender who calls himself Muntaqim (The Avenger), and more such attacks are to happen soon. He quickly puts together a crack team that includes his protégé, IG Cybercrime Vikrant Singh, and Major Shaina Verma of the National Security Guard. and gets to work trawling the dark web for more information on this mystery attack. Meanwhile, an angadia courier mysteriously jumps to his death when chased by the Railway police and far away in Pathankot, there are signs of a major attack being planned. A move by Vikrant and Mirza to bring forward the hacker backfires, leading to a second, bigger attack on Mumbai’s lifeline, the railway system. It is their first brush with cyberterrorism: a zero-day vulnerability in the Indian government’s system that could bring the country to its knees. But Muntaqim has a weapon in store that is even bigger… In Zero Day, racing against time and investigating a case unlike any other, Mirza and Vikrant face the most dangerous mission of their lives.