Eve Online is a cluster based MMO created primarily with Python.
The following statement is by Hilmar Veigar Petursson Chief Executive Officer of CCP games, on Python.org:
"Python enabled us to create EVE Online, a massive multiplayer game, in record time. The EVE Online server cluster runs over 50,000 simultaneous players in a shared space simulation, most of which is created in Python. The flexibilities of Python have enabled us to quickly improve the game experience based on player feedback" said Hilmar Veigar Petursson of CCP Games.
The following is a snapshot of the game:
We just added another snapshot because we thought that it looked nice :)
Python is known for its stability. Google utilizes Python for almost everything. That being the reason, the creator of Python is an employee @ Google.
What does it take to secure such MMO apps?
The main answer lies in the engines on which they are running. Python is known for its stability and highly structured with support to easy access/usage. Using Python does not mean that the software is secure, but that is just the first step towards "avoiding unstable development environment". The next thing is to ensure authenticity & authorization using access control techniques, integrity by using critificates, etc. But most of all MMO's main concern is to:
* Ensure that their model keeps changing, to avoid from someone cracking the software by applying Digital Rights Management solutions.
* Ensure that only authorized users get to access their tools.
* Prevent misuse by authorized users.
* Web application security - Prevent web based attacks.
* Load balance requests and have DoS/DDoS avoidances.
There are other things that MMO's do, to secure their apps. But these are the primary things I could think of. Beyond all this, Eve has done an awesome job and is the most popular MMO. Bravo Eve!