<< FinFisher malware is installed in various ways, including fake software updates, emails with fake attachments, and security flaws in popular software. Sometimes the surveillance suite is installed after the target accepts installation of a fake update to commonly used software.[2] Code which will install the malware has also been detected in emails.[17] The software, which is designed to evade detection by antivirus software, has versions which work on mobile phones of all major brands .>>

no backdoor is needed when a users behaviour will let you in. it helps greatly when the service provider co-operates