Black fax to harass large institutions or government departments, to retaliate against the senders of junk faxes, or merely as simple pranks. The basic principle of a black fax can be extended to form a "black fax attack." In this case, one or more sheets are fed halfway through the sender's fax machine and taped end to end, forming an endless loop that cycles through the machine. Not only can solid black be used, but also images which will repeat endlessly on the receiver's machine until its toner runs out. The introduction of computer-based facsimile systems (combined with integrated document imaging solutions)
Registered fax - The data (signed document and signature) are available to both parties, sender and receiver, in a confidentially secured environment. The data is securely archived so that it can serve as legal evidence in case of dispute between the parties. Registered faxes are stored in a secured web environment. The sender and the receiver can check the authenticity of the registered fax at any time in a secured web interface, as the fax is stored and archived for a long period of time. The following table defines the items to which each party in the registered fax process has access: