How to determine if a Flash Update Notification is Legitimate

Adobe Flash Player and Reader are some of the most popular Web plug-ins, and as a result malware developers commonly use them as a disguise for their programs. The recent Flashback malware is one example of this, where it originally was released as a fake update to Adobe Flash, and thereby confused a number of Mac users who installed it thinking it was a legitimate update they needed.

In order to notify Flash and Reader users of available updates, Adobe's software will display a notice regarding the availability of the new software; however, if you see such a notice then how will you know the update is legitimate or an attempt to install malware?