As if spam email wasn't intrusive and annoying enough, spammers might have a means at their disposal to send unwanted messages as print jobs to networked printers.

The attack - dubbed Cross Site Printing for Spamming - relies on abusing a built in (but seldom used) facility on networked printers after tricking users into visiting a maliciously-constructed website.

So all hackers would have to do is determine a printer's IP address, connect with it and force a termination that would cause the printer to spew out garbage. JavaScript trickery might be used to force the termination and subsequent HTTP Post or garbage to be printed, which might even be formatted using PostScript commands.

Other tricks including sending fax messages, formatting a printer's hard drive, or downloading new (potentially malicious) firmware may also be possible, security firm Trend Micro adds.

The network printer hijack attack is only a problem for printers connected via a local area network connection. Consumers who plug their printers directly into their PCs are not at risk.

Defending against the exploit involves keeping network printers secure. For example, admin passwords for printers should be established. It's also a good idea to limit print jobs processed to those originating from a centralised print server.

The attack is not printer specific and relatively simple. Attack vectors such as iFrame injection from compromised websites could make printer spam a big problem in future, Heise Security adds. ®

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• Adobe bends to might of US printers (2 August 2007)
• HP warns over printer hacking risk (6 April 2006)
• Is your printer spying on you? (29 July 2005)
• Letters Verisign DNS change broke my HP printer (17 September 2003)