black fax warningThere is no communication technology that is immune to malicious attacks, and faxing, while severely limiting the would-be attackers, still has several vulnerabilities that can be exploited, and black fax is probably one of the most damaging of all of the fax scams and attacks.

What is a Black Fax?

Black fax is an attack method that disables a fax machine in two ways – the receiver has to print out a fully black page over and over again, until the fax machine runs out of ink, and the line is busy for acceptance of new fax messages through the whole process.

Sometimes it's just several pages of black fax, but there were reports of a looped piece of black paper being used on the attacker's end, which basically completely paralyzes the attacked fax machine until it runs out of ink, or paper, or until it's mechanical components fail.

The most common black fax attacks are used as pranks, retribution and a crude sort of DoS attacks on fax machines.
Disgruntled ex-employees taking revenge, replies to annoying or spam fax messages and as general source of annoyance for the receiver – that's when black faxes are most commonly sent.

Avoiding Black Fax Messages

Now that you're aware of a potential vulnerability, you're most likely wondering how can you protect yourself in case of a black fax attack.
The problem is, there are not that many methods of dealing with this issue if you are using a fax machine – there's no method of prevention other than you noticing what's going on and interrupting the printing process.

Enterprise level fax machines with a server in front of them usually have filter systems that block out black fax attacks, and if you are not printing your receiving faxes but are storing them in the computer, the attack power is greatly diminished, but you still have a fax line that is kept busy by the attack and you still get spam messages on your hard drive.

The best defense altogether would be to use an online fax service or a PC with a fax modem for sending and receiving fax messages, which would reduce black faxes to nothing more than junk mail to be filtered in your folder.

Disclaimer: We do not support or advise the use of black faxes for any reason, this and other malicious attacks using faxing technology are listed only as examples, so the owners of fax machines can understand what kinds of problems can they face and how can they defend from them.

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