Read-and-write property specifying the security mode used when connecting to an OPC UA server. This property cannot be changed while communication is active. Possible values for this property are 1 - usmNone: Does not use any security mode in the connection (default), 2 - usmSign: Uses authentication in the connection, or 3 - usmSignAndEncrypt: Uses authentication and encryption in the connection. This property is used together with the SecurityPolicy property to determine the type of security of a connection.