class action

Last Thursday, HP CEO Enrique Lores addressed the company’s controversial practice of bricking printers when users load them with third-party ink. Speaking to CNBC Television, he said, “We have seen that you can embed viruses in the cartridges. Through the cartridge, [the virus can] go to the printer, [and then] from the printer, go to the network.”

That frightening scenario could help explain why HP, which was hit this month with another lawsuit over its Dynamic Security system, insists on deploying it to printers.

Dynamic Security stops HP printers from functioning if an ink cartridge without an HP chip or HP electronic circuitry is installed. HP has issued firmware updates that block printers with such ink cartridges from printing, leading to the above lawsuit (PDF), which is seeking class-action certification. The suit alleges that HP printer customers were not made aware that printer firmware updates issued in late 2022 and early 2023 could result in printer features not working. The lawsuit seeks monetary damages and an injunction preventing HP from issuing printer updates that block ink cartridges without an HP chip.

But are hacked ink cartridges something we should actually be concerned about?

To investigate, I turned to Ars Technica Senior Security Editor Dan Goodin. He told me that he didn’t know of any attacks actively used in the wild that are capable of using a cartridge to infect a printer.

Goodin also put the question to Mastodon, and cybersecurity professionals, many with expertise in embedded-device hacking, were decidedly skeptical.

Another commenter, going by Graham Sutherland / Polynomial on Mastodon, referred to serial presence detect (SPD) electrically erasable programmable read-only memory (EEPROM), a form of flash memory used extensively in ink cartridges, saying:

I’ve seen and done some truly wacky hardware stuff in my life, including hiding data in SPD EEPROMs on memory DIMMs (and replacing them with microcontrollers for similar shenanigans), so believe me when I say that his claim is wildly implausible even in a lab setting, let alone in the wild, and let alone at any scale that impacts businesses or individuals rather than selected political actors.

HP’s evidence

Unsurprisingly, Lores’ claim comes from HP-backed research. The company’s bug bounty program tasked researchers from Bugcrowd with determining if it’s possible to use an ink cartridge as a cyberthreat. HP argued that ink cartridge microcontroller chips, which are used to communicate with the printer, could be an entryway for attacks.

As detailed in a 2022 article from research firm Actionable Intelligence, a researcher in the program found a way to hack a printer via a third-party ink cartridge. The researcher was reportedly unable to perform the same hack with an HP cartridge.

Shivaun Albright, HP’s chief technologist of print security, said at the time:

A researcher found a vulnerability over the serial interface between the cartridge and the printer. Essentially, they found a buffer overflow. That’s where you have got an interface that you may not have tested or validated well enough, and the hacker was able to overflow into memory beyond the bounds of that particular buffer. And that gives them the ability to inject code into the device.

Albright added that the malware “remained on the printer in memory” after the cartridge was removed.

HP acknowledges that there’s no evidence of such a hack occurring in the wild. Still, because chips used in third-party ink cartridges are reprogrammable (their “code can be modified via a resetting tool right in the field,” according to Actionable Intelligence), they’re less secure, the company says. The chips are said to be programmable so that they can still work in printers after firmware updates.

HP also questions the security of third-party ink companies’ supply chains, especially compared to its own supply chain security, which is ISO/IEC-certified.

So HP did find a theoretical way for cartridges to be hacked, and it’s reasonable for the company to issue a bug bounty to identify such a risk. But its solution for this threat was announced before it showed there could be a threat. HP added ink cartridge security training to its bug bounty program in 2020, and the above research was released in 2022. HP started using Dynamic Security in 2016, ostensibly to solve the problem that it sought to prove exists years later.

Further, there’s a sense from cybersecurity professionals that Ars spoke with that even if such a threat exists, it would take a high level of resources and skills, which are usually reserved for targeting high-profile victims. Realistically, the vast majority of individual consumers and businesses shouldn’t have serious concerns about ink cartridges being used to hack their machines.