Black fax
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The term black 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). An added 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. 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.
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.
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.