Sudoers and root

Issue

• The sudoers on this system is set to < group ALL=ALL >
• All the users in the group are allowed to use any command with sudo.
• But we dont want the user to be able to user su - or su -i etc... to gain root shell.
• That can be done by excluding these commands in sudoers.
• But we would like to prevent users from been able to escape the shell they are in and getting access to root shell.
• For an example a user does sudo vi then types :sh this will get him/her root shell. is there a way for preventing this type of escapes?