Some mobile phone software we installed needs to be read and written into the user database before it can run. If it is read and written into the user database by malicious software, the system will malfunction or be infected with virus. Therefore, for the sake of security, mobile phones are not allowed to read and write software to the user database except for some programs that will not harm the mobile phone system (that is, signature software). This software can run normally. If it is not a signed program, and the program must be read and written to the user database before it can run, it should be because it is not a correct program, and reading and writing may be harmful to the mobile phone system, so the mobile phone does not allow its software to read and write to the user database, so the program cannot run. However, most of the software on the Internet is unsigned now.