We haven't really implemented any kind of anti-modification mechanism to saved games. However, the Ren'Py developers are implementing security measures, since there have been cases of virus propagation through saved games (although I really don't know how).
I could even share a saved game of mine with you, and a notification will appear that it could be a malicious file.
Our variables are way too easy to detect and can be easily modifided with online services, but, very early on (2 years ago), we did tried to protect the game variables, but the players still found a way to break the protections, so we said "fuc... it, let just leave it like that", we just want to create a good game that players can enjoy, and if some players want to cheat, its okay

ist part of the game too.