Imagine you are a programmer who deliberately left an opening in a piece of code during the build phase that allows you an unknown entry into the application. Using this opening in the code, which of the following types of attack could hackers use to gain unauthorized access to the application ?

A backdoor is a deliberately placed hidden access point in software that bypasses normal authentication mechanisms. As described in the scenario, a programmer could leave an opening during the build phase that allows unauthorized entry later. Attackers can discover and exploit these backdoors to gain unauthorized access to the application or system. Birthday attacks exploit hash collisions, man-in-the-middle attacks intercept communications, and spoofing involves forging identities - none of which match the scenario of a deliberate code opening.