Chandigarh, Oct. 6 -- Six schools in Sectors 15, 28, 31, 39, 41 and 45 received bomb threats, triggering a thorough search operation by the police, along with the bomb squad, on Monday morning. Nothing suspicious was found, officials said. Police said multiple calls have been received this year threatening private and government schools, the Punjab and Haryana secretariat, the high court and the district courts complex, but the accused in most of the cases remain untraceable. A senior police officer, wishing not to be named, said perpetrators use special apps to send emails that keep the identity of the sender anonymous. They also use Virtual Private Network (VPN) settings to route their internet traffic through different countries, making it difficult to track them, the official said....