Apple is urging customers to update their devices after a significant security flaw was discovered.
On Monday, Apple posted a security note saying that malicious PDF files could exploit a flaw in software.
"Processing a maliciously crafted PDF may lead to arbitrary code execution. Apple is aware of a report that this issue may have been actively exploited."
The spyware is called "Pegasus" and is believed to have been used to exploit devices since at least February of this year, according to CNET.
Apple head of security engineering and architecture operations Ivan Krstic said in a statement, "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. While that means they are not a threat to the overwhelming majority of our users, we continue to work tirelessly to defend all our customers, and we are constantly adding new protections for their devices and data."