The impact of WannaCry ransomware attack has been limited to five or six isolated instances so far and there are no reports of any substantial disruption to India's IT backbone, the government said today. A multi-agency monitoring team is continuously assessing the situation round the clock, IT Secretary Aruna Sundararajan said on the margins of a Broadband India Forum event. CERT-In, the government's cyber security arm, has maintained that apart from five or six isolated instances, there are no reports of a substantial scale to indicate that Indian systems have been hit. "One such incident pertains to 18 computers of Andhra Pradesh Police. and apart from that, there are five other cases. one of them in Kerala where some of the panchayat computers were affected," Sundararajan said. All the cases reported so far involve fragmented, and isolated systems or standalone machines, she stressed. "Since March, the government has been on high alert. We have already installed the necessary security patches as far as the key networks are concerned. We have not got any reports of widespread infection of the ransomware," she said. Over the last few days, the global ransomware attack WannaCry infected computers running on older versions of Microsoft operating systems like XP, locking access to files. The cyber criminals have demanded a fee of about USD 300 in crypto-currencies like Bitcoin for unlocking the device. Reports suggest that over two lakh systems globally could have been infected by the malicious software. The ransomware has hit various IT systems in more than 150 countries, including Russia and the UK, in one of the most widespread cyber attacks in history.