A variety of firewall, VPN, and spam filtering gear sold by Barracuda Networks contains undocumented backdoor accounts that allow people to remotely log in and access sensitive information, researchers with an Austrian security firm have warned.

The SSH, or secure shell, backdoor is hardcoded into "multiple Barracuda Networks products" and can be used to gain shell access to vulnerable appliances, according to an advisory published Thursday by SEC Consult Vulnerability Lab.

"This functionality is entirely undocumented and can only be disabled via a hidden 'expert options' dialog," the advisory states. The boxes are configured to listen for SSH connections to the backdoor accounts and will accept the username "product" with no Update: a "very weak" password to log in and gain access to the device's MySQL database. While the backdoors can be accessed by only a small range of IP addresses, many of them belong to entities other than Barracuda.

"The public ranges include servers run by Barracuda Networks Inc. but also servers from other, unaffiliated entities—all of whom can access SSH on all affected Barracuda Networks appliances exposed to the Internet," the advisory explained.

Barracuda issued several of its own security advisories on Wednesday here. "Our research has confirmed that an attacker with specific internal knowledge of the Barracuda appliances may be able to remotely log in to a non-privileged account on the appliance from a small set of IP addresses," one advisory with a risk rating of "medium" stated. "The vulnerabilities are the result of the default firewall configuration and default user accounts on the unit."

A timestamp and version relevant for the code that enables the backdoor bears a date from 2003, suggesting it may have existed in the Barracuda appliances for a decade. Advisories from SEC Consult and Barracuda also reference a serious authentication bypass bug. In an age of sophisticated advanced persistent threats, administrations who oversee any of this gear should update as soon as possible.

Story updated to correct sentence about password required to log in to the "product" account. Once logged in, no password is required to access the MySQL database. Thanks to SEC Consult's Johannes Greil for the correction.