Some iOS security experts say this is yet another incident that shows iOS is so locked down it’s hard—if not impossible—to figure out if your own iPhone has been hacked. “The simple reality is there are so many 0-day exploits for iOS,” Stefan Esser, a security researcher that specializes in iOS, wrote on Twitter. Several iOS security researchers who spoke with Motherboard agree that the iPhone is too locked down for its own good. Jonathan Levin, a researcher who has written books about iOS exploitation and provides training on iPhone security, said that in his opinion, so few iOS zero-days have been caught because they are worth a lot of money, and thus rarely used. But unless Apple makes fundamental changes in how iOS is architected, “there is no practical way to tell an iPhone got ‘infected,’” according to a security researcher who goes by the alias Xerub, and who is the organizer of 0x41, an iOS only conference.