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)
Junk Fax Prevention Act of 2005 of nuisance telemarketing tactics, it included provisions making it illegal for any person to send an unsolicited advertisement to a fax machine. The law further authorized the recipient of a fax sent in violation of the statute (or a regulation promulgated under the statute) to sue the sender in state court to enjoin further violation, recover for actual monetary losses from such a violation, $500 in statutory damages for each violation (whichever is greater), or both. The law also allows the court, in its discretion, to treble these damages if it finds the defendant violated the statute "willfully" or "knowingly."