Individuals with iPads and iPhones are encouraged to update their devices as soon as they can.

Apple, on Monday, updated its software for iPhones in response to a vulnerability that experts believe has been exploited by surveillance software, CNN reports.

The news outlet reports that information from the University of Toronto's Citizen Lab reveals exploitation of the software may have started in February. 

The group explained that hackers were able to infiltrate a user's phone without the user clicking on any links. 

The spyware is called Pegasus and was created by an Israeli firm called NSO Group, an agency that allegedly engaged in the surveillance of journalists and human rights activists in multiple countries.

In the past, NSO has said its software is only sold to vetted customers for counterterrorism and law enforcement purposes, but researchers say this claim is false and allege they've found multiple cases in which the spyware was deployed on dissidents or journalists.

In 2019, for example, Citizen Lab analysts said Pegasus was used on the mobile phone of the wife of a slain Mexican journalist.

It's in response to the alleged actions of NSO that Apple created a plug for the hole in its iMessage software that would have previously allowed hackers to infiltrate phones.

"Attacks like the ones described are highly sophisticated, cost millions of dollars to develop, often have a short shelf life, and are used to target specific individuals," Ivan Krstic, head of Apple Security Engineering and Architecture, said in a statement.

Krstic said Apple was swift in addressing the issue and the vulnerability is "not a threat to the overwhelming majority of our users."

Even so, security experts are encouraging iPhone users to update their mobile devices as a precautionary measure.