Criminals can compromise company networks by sending malicious faxes

Check Point has revealed details about the two critical remote code execution vulnerabilities (CVE-2018-5924, CVE-2018-5925) it discovered in the communication protocols used in tens of millions of fax devices globally.

A fax number is all an attacker needs to exploit the flaws, and potentially seize control of a company or home network.

malicious faxes network compromise

The Check Point research demonstrated the vulnerabilities in the popular HP Officejet Pro All-in-One fax printers.

The same protocols are also used by many other vendors’ faxes and multifunction printers, and in online fax services such as fax2email, so it is likely that these are also vulnerable to attack by the same method.

About Faxploit

Usually seen as outdated technology, there are over 45 million fax machines in use in businesses globally, with 17 billion faxes sent every year.

It is still widely used in several Industry sectors such as healthcare, legal, banking and real estate, where organizations store and process vast amounts of highly sensitive personal data. The UK’s National Health Service alone has over 9,000 fax machines in regular use for sending patient data. In many countries, emails are not considered as evidence in courts of law, so fax is used when handling certain business and legal processes. Nearly half of all laser printers sold in Europe are multifunction devices with fax capability.

Once an attacker obtains an organization’s fax number (which is easily obtainable from corporate websites), the attacker sends a specially created image file by fax to the target. The vulnerabilities enable malware (such as ransomware, crypto-miners or spyware) to be coded into the image file, which the fax machine decodes and uploads to its memory. The malware can then potentially breach sensitive data or cause disruption by spreading across any networks to which the fax machine is connected.

Here’s a demonstration of the attack:

Prevent exploitation

To minimize the security risk, Check Point advises that organizations check for available firmware updates for their fax devices and apply them.

“We worked closely with HP to fix the vulnerability and, following the process of responsible disclosure, they managed to release a patch before this publication. In fact, if your device is already configured to auto-update then the patch has likely already been applied. This patch, however, only applies to HP all-in-one printers and the vulnerability may well still apply to devices from other manufacturers as well,” the researchers noted.

Businesses are also urged to place fax devices on a secure network segment separated from applications and servers that carry sensitive information.

“Once unauthorized access is gained, network segmentation can provide effective measures to mitigate the next stage of intrusion into a network and limit the spread of the attack by lateral movement across it,” they explained.

The good news is that there’s no indication that the vulnerabilities are being exploited in the wild.

“Many companies may not even be aware they have a fax machine connected to their network, but fax capability is built into many multifunction office and home printers,” said Yaniv Balmas, Group Manager, Security Research at Check Point. “This groundbreaking research shows how these overlooked devices can be targeted by criminals and used to take over networks to breach data or disrupt operations.

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