This is where code signing comes into it. When you open a quarantined app, Gatekeeper checks to see whether it complies with you computer's security policy subsystem. It's entirely possible that the difference you're seeing between different computers has to do with how the disk image was downloaded and therefore whether the apps are quarantined. To check whether a file is quarantined, use ls on it and look for the attribute. dmg file, it gets marked as quarantined when you open it, the attribute gets propagated to its contents, so the app is also marked as being in quarantine (and if you copy it to /Applications, the quarantine attribute gets copied along with everything else). Also, command-line tools like curl and wget won't apply quarantine. AFP or SMB) with the Finder will not mark it as being in quarantine.

For example, copying a file over a file sharing connection (e.g. Other types of internet apps (email, chat, etc) should also attach this attribute to downloaded files.īut not all network download methods will apply the quarantine attribute. When you download a file with a browser, the browser will attach a attribute to it, indicating that it came from an untrusted network source. Quarantine is a result of the app (or the disk image it was in) being downloaded. Let me explain these two things in more detail. The error you're seeing is from Gatekeeper, and indicates two different (and independent) things: 1) the app is quarantined (which has to do with how it was downloaded, not how it's signed) and 2) it is not signed in a way that complies with the Gatekeeper policy defined in Security & Privacy preferences.

I think you may be a bit confused about how quarantine, code signing, and Gatekeeper work.

Mac gatekeeper settings