The app you tried to open was not registered with Apple by an identified developer. This doesn’t necessarily mean that something’s wrong with the app. For example, some apps were written before developer ID registration began. However, the app has not been reviewed. Also, there is no way for OS X to check whether the app has been modified or broken since it was released. A common way to distribute malware is to take an innocent app and insert harmful code into it, and then redistribute the infected app.
The safest approach is to look for a newer version of the app from the Mac App Store or check for an alternative from an identified developer.
In addition to apps, other types of files may not be safe. Scripts, web archives, and Java archives have the potential to cause harm to your system. Of course, not all files like this are unsafe, but you should exercise caution when opening any such downloaded file. An alert appears when you first try to open these files.
You can choose to override your security settings and open the app anyway.
- In the Finder, locate the app you want to open. Most apps can be found in the Applications folder.
- Press the Control-key and click the app icon.
- Choose Open from the pop-up menu.
- Click Open.
The app will be stored as an exception to your security settings, and you will be able to open it in the future by double-clicking it.