Exploiting Linux authentication

Linux authentication works in a similar fashion as the Windows login process. At the login screen or prompt, the user enters their login ID followed by their password. The system searches the local database for a user that matches the entry. If the user is found, the system checks the password against the database. If the authentication is successful, the attributes of the user profile are enabled and the user is logged in; otherwise, a failure message is returned.

The ultimate goal of the attacker is to get the highest privileges they can. For Linux systems, that is getting to the root account. This account can be seen as the equivalent of the Windows administrator account, which allows complete control of the system. But before they can do that, they first have to get on to the system with an account. The first way is to exploit a specific service or application running on the server. We will discuss that method in greater detail in Chapters 7 and...