。Untrusted developer -the prevalence of installed applications coming from unknown developers 。Open app markets raising concerns about how risky third-party applications are and how they may misuse or improperly handle users'privacy-sensitive data • Untrusted developer – the prevalence of installed applications coming from unknown developers • Open app markets – raising concerns about how risky third-party applications are and how they may misuse or improperly handle users’ privacy-sensitive data