The news was abuzz yesterday with coverage of a study released by Columbia University researchers warning consumers that HP laser printers are wide open to remote tampering and hacking. The researchers claim that the vast majority of printers from HP’s LaserJet line accept firmware updates without checking for any sort of digital authentication, allowing malicious users to abuse the machines remotely. The researchers go so far as to claim that modified firmware can be used to overheat the printer’s fuser, causing fires, to send sensitive documents to criminals, and even force the printers to become part of a botnet.

Officials at HP were quick to counter the claims, stating that all models built in 2009 and beyond require firmware to be digitally signed. Additionally, they say that all of the brand’s laser printers are armed with a thermal cutoff switch which would mitigate the fuser attack vector before any real fire risk would present itself. Despite HP’s statements, the researchers stand by their claims, asserting that vulnerable printers are still available for purchase at major office supply stores.

While most external attacks can easily be prevented with the use of a firewall, the fact that these printers accept unsigned firmware is undoubtedly an interesting one. We are curious to see if these revelations inspire anyone to create their own homebrew LaserJet firmware with advanced capabilities (and low toner warning overrides), or if this all simply fizzles out after a few weeks.

[Sprite_tm] sent us his latest project. He has found a way to display custom messages on a laserjet printer without a computer.   He’s using an ATTiny2313 to send signals through a parallel port. This project is so cheap and quick to install it could be disposable. Just program your message before hand, pop it on and walk away.

Using nothing more than a phillips head screwdriver and a small lever to push tricky plastic tabs, the team removed every single component from the printer until nothing was left. After removing the rear panel and a pair of medium circuit boards that control most of the printer’s functions, they found this unique item: a humidity sensor.

They removed several more parts, including the small PCB with transparent circuits that holds the LCD, the power board, the entire belt assembly, and several gears and motors. This brought them to the optics box containing two boards like the one above. The rear sides of the boards each have two laser diodes and one photodiode that is likely used in synchronizing data with the position of the page being printed. The optics box also yielded mirrors that reflect the laser, the motors that turn the mirrors, and several lenses, including a plastic molded lens assembly with three different lenses built into it.

When they were through with the optics package, the team moved on to the fuser assembly. Instead of using a quartz lamp to melt the toner like many other printers, this one contains a film resistive ceramic heater inside one of the rollers. After disassembling the fuser assembly, there was only one board left inside the remaining steel shell.

Evil Mad Scientist Labs posted more than 200 pictures in a Flickr photoset (all photos by [Windell H. Oskay]) showing every step of the process, and at the end of their article they list all the usable parts they got from the teardown. Taking apart the printer is only half the fun, though; we’re looking forward to what they build next.