Applications can be distributed to Macs and installed by the user from any source and by any method such as downloading (with or without code signing, available via an Apple developer account) or through the Mac App Store, a marketplace of software maintained by Apple through a process requiring the company's approval. Apps installed through the Mac App Store run within a sandbox, restricting their ability to exchange information with other applications or modify the core operating system and its features. This has been cited as an advantage, by allowing users to install apps with confidence that they should not be able to damage their system, but also as a disadvantage due to blocking the Mac App Store's use for professional applications that require elevated privileges. Applications without any code signature cannot be run by default except from a computer's administrator account.