The term black fax (also known as a mobius fax) refers to a prank fax transmission, consisting of one or more pages entirely filled with a uniform black tone. The sender's intention is typically to consume as much of the recipient's fax ink or toner as possible, thus denying its owner its use (this is similar to computer-based denial of service attacks). A bonus (for the malicious sender) is that, in cases where the receiving fax machine prints the fax using water-based ink onto conventional paper, the saturated paper may disintegrate inside the fax machine's mechanism, thus entirely blocking it. (Obviously this doesn't bother thermal faxes) Black faxes can be particularly effective as the CCITT fax algorithm compresses the solid black image very well - so a very short fax call can produce many pages. Fax (short for facsimile - from Latin fac simile, make similar, i. ... A denial-of-service attack (also, DoS attack) is an attack on a computer system or network that causes a loss of service to users, typically the loss of network connectivity and services by consuming the bandwidth of the victim network or overloading the computational resources of the victim system. ... ITU-T is the telecom standardization organization of the International Telecommunication Union (ITU). ...

Black faxes have been used to harass large institutions or government departments, to retaliate against the senders of junk (spam) faxes, or merely as simple pranks. A KMail folder full of spam emails collected over a few days. ...

The basic principle of a black fax can be extended to form a fax attack. In this case, a single sheet is 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 their toner runs out.

The introduction of computer-based facsimile systems (combined with integrated document imaging solutions) at major corporations now means that black faxes are unlikely to cause problems for larger corporations.

Black faxes are similar (both in intention and implementation) to lace cards. A lace card from the early 1970s. ...