Today it's come into the spotlight with the biggest bounty ever publicly offered for a single such exploit: $1 million for a technique that can break into an iPhone or iPad running Apple's freshly released iOS 9.

On Monday, a new security industry firm known as Zerodium announced that it will pay that seven-figure sum to anyone who gives the company a hacking technique that can take over an iOS device remotely, via a web page the victim visits, a vulnerable app on the victim's device, or by text message. The company says it's willing to pay the bounty multiple times, though it may cap the payouts at $3 million.

"Due to the increasing number of security improvements and the effectiveness of exploit mitigations in place, Apple's iOS is currently the most secure mobile OS," reads the statement on Zerodium's website announcing the bounty. "But don't be fooled, secure does not mean unbreakable, it just means that iOS has currently the highest cost and complexity of vulnerability exploitation and here's where the Million Dollar iOS 9 Bug Bounty comes into play."