T 5.140 Evaluation of residual information in printers, copiers, and all-in-one devices

Many digital copiers, printers, and all-in-one devices are equipped with a large amount of internal storage. If a document is output more than once, then it is more efficient to read in the source document or send it to the device only once. The document is digitized (if it is not already available in digital form), stored in the storage unit of the device, and can then be reproduced directly from there.

There are two types of storage used in this case: volatile and non-volatile storage. In volatile storage, the data is deleted as soon as the supply voltage is disconnected. In contrast to volatile storage, the information saved in non-volatile storage is stored permanently, meaning it can also be read even after the device has been switched off. Examples of non-volatile storage are hard disks and flash memory.

Depending on the method of operation and configuration of the device, the storage contents can be deleted by various events. Deletion may be possible as soon as the next document is read, or maybe only once storage space is needed.

When information is saved in storage, unauthorised persons may be able to access this information under some circumstances. In the simplest case, it may only be possible to print the last document saved. A greater problem is posed when an attacker is able to read out the entire storage device for analysis purposes.

Even if the stored information is deleted directly after use, it may be possible to reconstruct the data under certain circumstances. Not every device overwrites the deleted data after deletion. Overwriting the storage space used by the deleted data would make restoration of the deleted data significantly more difficult.

Digital copiers and printers are often only leased. After the time period agreed to, the device is then returned and possibly replaced by a newer device. All subsequent owners or leasers of the device could therefore obtain access to any information still present in the storage device.