Well just recently researchers discovered a campaign installing backdoors on iPhones using a chain of several 0-day expoits or in this case using also 0-click exploits, where no interaction from a user is needed. However those attack chain are so advanced that practically normal law enforcement would never be able to do it. But theoretically yes some well equiped state actors are able to infect you without noticing. If you are really intrested to see how advanced these attack are search for “project triangulation” or watch the recording from last years chaos computer conference: …ccc.de/…/37c3-11859-operation_triangulation_what…