What is squawk 7500, the 'hijack' code issued amid flydubai flight scare?

A Dubai-Israel flydubai flight triggered security alert after it transmitted squawk 7700, followed by squawk 7500. Squawk 7500 is an internationally recognised transponder code indicating unlawful interference involving an aircraft. It's commonly associated with possible hijacking. It can alert ATC that aircraft may've been taken over or crew is facing unlawful security situation.