Complex sentence: The term hackproof has been used for some time to assert that a product 1 or system 2 has a characteristic--immunity to unauthorized remote access and manipulation--that is mathematically impossible to achieve on a networked general-purpose computer.
Split into simpler sentences: The term hackproof has been used for some time to assert that a product 1 or system 2 has a characteristic--immunity to unauthorized remote access and manipulation. This characteristic is mathematically impossible to achieve on a networked general-purpose computer.