The firm behind the Pegasus spyware has been ordered to pay WhatsApp $167m (£125m) for hacking 1,400 people in 2019.
Pegasus is malicious software which can be installed remotely on mobile phones to access, among other things, people's microphones and cameras.
NSO Group, which sells the tech, has been accused of enabling authoritarian regimes to monitor journalists, activists and even political figures.
WhatsApp owner Meta said it marked the "first victory against the development and use of illegal spyware".
NSO said it would "carefully examine the verdict's details and pursue appropriate legal remedies, including further proceedings and an appeal“.