Researchers have been demonstrating attacks against printers for years. Now, Hewlett-Packard has started building defences directly into its printers’ firmware instead of just patching individual vulnerabilities.
The company’s new M506, M527, and M577 series of LaserJet Enterprise printers, set to go on sale in October and November, will have built-in detection for unauthorised BIOS and firmware modifications.
HP refers to this capability as “self-healing security,” but it is actually a set of code integrity checking mechanisms that security researchers have asked embedded systems manufacturers to implement for years.
One of the new features, called HP Sure Start, validates the integrity of the BIOS code at boot time, and if any modification is detected it reboots the device and loads a clean copy. This is based on a similar feature that HP’s Elite line of PCs have had since 2013.
The BIOS is the low-level software that is responsible for initialising hardware components and booting the operating system.
Another new security feature that HP calls whitelisting is an integrity checking mechanism for the FutureSmart firmware, the OS of HP LaserJet enterprise printers. It ensures that the firmware code has not been tampered with and is digitally signed by HP before loading it into memory.
Finally, the new printers also include a run-time intrusion detection system that monitors memory operations while the printers are in use and checks for signs of potential compromise. If an intrusion is detected, the device is rebooted.
The good news is that these security features can also be added to older printers. All HP LaserJet Enterprise printers that have been released since April will be able to benefit from them through a firmware update.
Older LaserJet Enterprise and OfficeJet Enterprise X printers that have been launched since 2011 will only get the whitelisting and intrusion detection mechanisms through a FutureSmart service pack update.
While HP should be commended for adding these security features, attacks against printers, including those that modify the firmware, have been known for years. Hopefully at some point these mechanisms will also be added to future consumer and small-business printer models.
In 2011, two researchers from Columbia University found that attackers could rewrite the firmware on many HP LaserJet printers with a malicious version by simply embedding the commands and code in a document sent to be printed. The attack was possible because the printers did not validate firmware updates.
The lack of digital signature verification for firmware is a problem that has plagued embedded devices for years and many devices are being still engineered today without such basic protections. Just recently, researchers discovered an ongoing attack that replaces the firmware on Cisco business-grade routers with a backdoor-equipped version.
Aside from replacing the entire firmware, attackers can also exploit vulnerabilities in individual firmware components to gain unauthorised access to a device’s functions or the files stored on it.
For example, in 2009, HP issued firmware updates for several LaserJet printer models in order to fix a remotely exploitable vulnerability in their Web-based administration interface.
Lucian Constantin, IDG News Service
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