In September 2018, The Citizen Lab, a Canadian cybersecurity organisation, published a comprehensive report identifying 45 countries, including India, in which the spyware was being used.   https://citizenlab.ca/2018/09/hide-and-seek-tracking-nso-groups-pegasus-spyware-to-operations-in-45-countries/ 

Between August 2016 and August 2018, we scanned the Internet for servers associated with NSO Group’s Pegasus spyware. We found 1,091 IP addresses that matched our fingerprint and 1,014 domain names that pointed to them. We developed and used Athena, a novel technique to cluster some of our matches into 36 distinct Pegasus systems, each one which appears to be run by a separate operator...Our findings paint a bleak picture of the human rights risks of NSO’s global proliferation. At least six countries with significant Pegasus operations have previously been linked to abusive use of spyware to target civil society, including Bahrain, Kazakhstan, Mexico, Morocco, Saudi Arabia, and the United Arab Emirates.

This article gives some technical details..on how it is done.. 

This report identifies 45 countries with suspected Pegasus spyware infections operated by at least 33 likely NSO customers. We determined this by performing DNS cache probing on domain names we extracted from command and control (C&C) servers matching a newly devised fingerprint for Pegasus. We grouped the C&C servers, with each group representing a single Pegasus operator (assumed to be an NSO customer) using a technique that we call Athena. The resulting global map of NSO Pegasus infections reveals several issues of urgent concern.
Known spyware abusers operating Pegasus 

While some NSO customers may be using Pegasus spyware as part of ‘lawful’ criminal or national security investigations investigations, at least six countries with significant Pegasus operations have a public history of abusing spyware to target civil society.

Widespread cross-border surveillance with Pegasus

Ten Pegasus operators appear to be conducting surveillance in multiple countries. While we have observed prior cases of cross-border targeting,

Failures at due diligence, contribution to global cyber insecurity

The cases identified in this report raise serious doubts as to the depth and seriousness of NSO’s due diligence and concern for human rights protections. They also suggest that the company has a significant number of customers that maintain active infections in other countries, likely violating those countries laws.

Reckless Exploit Mexican Journalists, Lawyers, and a Child Targeted with NSO Spyware https://citizenlab.ca/2017/06/reckless-exploit-mexico-nso/

https://tspace.library.utoronto.ca/bitstream/1807/96731/1/Report%2393--recklessexploit.pdf

What is Pegasus spyware and how does it hack phones? https://amp.theguardian.com/news/2021/jul/18/what-is-pegasus-spyware-and-how-does-it-hack-phones David Pegg and Sam Cutler
Sun 18 Jul 2021  NSO Group software can record your calls, copy your messages and secretly film you 

Huge data leak shatters the lie that the innocent need not fear surveillance The Pegasus project is a collaborative reporting project led by the French nonprofit organisation Forbidden Stories, including the Guardian and 16 other media outlets. For months, our journalists have been working with reporters across the world to establish the identities of people in the leaked data and see if and how this links to NSO’s software. 

Few pause to think that their phones can be transformed into surveillance devices, with someone thousands of miles away silently extracting their messages, photos and location, activating their microphone to record them in real time.

Such are the capabilities of Pegasus, the spyware manufactured by NSO Group, the Israeli purveyor of weapons of mass surveillance.

NSO rejects this label. It insists only carefully vetted government intelligence and law enforcement agencies can use Pegasus, and only to penetrate the phones of “legitimate criminal or terror group targets”.

For more on Pegasus Affair: http://emeets.lnwr.in/index.php/me-mes-for-civil-liberties/surveillance/99-pegasus-affair

Pegasus Project Explained: How Ministers, Politicians, Journalists in India Have Been Spied On https://www.youtube.com/watch?v=RXlc_uFxVZY   300 people we know of 16 institutions, 80 jounralist, 

A review of the leaked database by The Wire and partner news organisations shows that at least nine numbers belonged to eight activists, lawyers and academics arrested between June 2018 and October 2020 for their supposed role in the Elgar Parishad case.

Pegasus Project: How Phones of Journalists, Ministers, Activists May Have Been Used to Spy On Them https://thewire.in/government/project-pegasus-journalists-ministers-activists-phones-spying 
An international collaborative reporting project has established the frightening extent to which governments around the world, including India, could be using surveillance tools in ways that have nothing to do with national security.

Senior lawyer Mihir Desai, who is representing several persons arrested in the case, said that this attack can’t be looked at as “simple surveillance”. “It goes beyond surveillance, it is actually interference with the person’s life. The malware is planted to get control over the person’s data and life,” Desai told The Wire. In the absence of a clear data protection law, it has become a nightmare to defend these cases in court, Desai added.

Phones Of Journalists, Politicians Hacked Using Spyware in 2017-2019: Report https://www.youtube.com/watch?v=mbPhZKmsAy4 Phone numbers of Indian ministers, opposition leaders and journalists have been found on a leaked database of targets for hacking that used Israeli spyware 'Pegasus', reported news website The Wire and other publications this evening. Members of the legal community, businessmen, government officials, scientists, rights activists and others are also in the list of over 300 verified Indian mobile telephone numbers, the reports said.

2 Ministers, 40 Journalists, 3 Opposition Figures Targeted By Spy Software: Report https://www.youtube.com/watch?v=PYR-MC7Bh00 Phone numbers of Indian ministers, opposition leaders and journalists have been found on a database of targets for hacking that used Israeli spyware 'Pegasus' - only available to governments - reported The Wire and other publications this evening.