PEGASUS is spyware developed by NSO Group, an Israeli cyber intelligence company that sells exclusively to governments. The technical capability described is accurate and the delivery mechanism is what makes it genuinely alarming.
Zero-click exploitation is the defining characteristic. Most malware requires you to do something. Click a link. Open an attachment. Approve a permission. Pegasus exploits vulnerabilities in the processing layer of applications, specifically iMessage, WhatsApp, and Apple Music on iOS, that trigger simply by receiving a message. The malicious payload executes at the moment the message is received and processed by the OS. You do not see a notification. You do not interact with anything. Your phone is compromised before you are aware a message arrived.
Once installed Pegasus operates at the deepest level of the operating system with root access. It can read encrypted messages after decryption on the device, meaning Signal and WhatsApp end-to-end encryption is bypassed entirely because Pegasus reads the message after it has already been decrypted for display. It activates the microphone and camera silently. It extracts location history, contacts, emails, call logs, and browser history. It can exfiltrate data over Wi-Fi to avoid unusual cellular data patterns.
The Pegasus Project investigation published in July 2021 involved Forbidden Stories, Amnesty International, and 17 news organisations analysing a leaked list of over 50,000 phone numbers identified as persons of interest by NSO Group clients. The list included journalists at major publications, heads of state, lawyers, human rights activists, and business executives across 45 countries.
Forensic analysis by Amnesty International's Security Lab confirmed Pegasus infections on devices belonging to journalists and activists. Apple subsequently sued NSO Group and began issuing threat notifications directly to users whose devices showed evidence of state sponsored spyware attacks.
The verified targets included the phones of people close to Jamal Khashoggi before his murder. French President Emmanuel Macron was on the list. So were heads of state from multiple countries, some of which were supposedly clients of NSO Group themselves.
NSO Group maintains Pegasus is sold only to vetted government clients for legitimate law enforcement and counter-terrorism purposes, but guess what?
Some how Pegasus still got to our hands and available for top hackers like us.
I can teach you more about this spyware if interested in it.
Alert: Pegasus Spyware Returns Smarter, Stealthier, and Harder to Detect! 
