Embedded Web Servers Exposing Organizations To Attack

A researcher who has been scanning the Internet for months looking for unsecured, embedded Web servers has found a bounty of digital scanners, office printers, VoIP systems, storage devices, and other equipment fully exposed and ripe for attack.

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Michael Sutton, vice president of security research for Zscaler Labs, at Black Hat USA 2011 next month will demonstrate his findings: Ricoh and Sharp copiers, HP scanners, and Snom voice-over-IP (VoIP) phones were the most commonly discovered devices, all accessible via the Internet. "It was pretty shocking to me: Virtually none of these should be exposed to the Internet. There's not a good reason that an HP scanner should be exposed to the Net," Sutton says.

It's a recipe for disaster: Embedded Web servers with little or no security get misconfigured when they're installed. Most likely, the potential victims are small to midsize businesses or consumers with less technical expertise who misconfigure their devices and have no idea they're showing up online. "They're taking this device, plugging it into the wall, and making a mistake on a router or access point ... and suddenly things are exposed to the Web," he says.

Sutton used Amazon EC2 computing resources to constantly scan large blocks of addresses and to detect any embedded Web servers. Sharp and Ricoh copiers digitally archive past photocopies, he notes, so if that feature is enabled and the copier is sitting on the Net unsecured, an attacker could retrieve any previously photocopied documents, he says. Even the fax-forwarding feature in some HP scanners could be abused if the scanner were open to the Internet: An attacker could access any faxed documents to the user by having them forwarded to his fax machine, for example.

The Snom VoIP systems that Sutton found in his Internet scans could be vulnerable to eavesdropping or pilfered caller information. "Some of their VoIP systems have a kind of admin debugging/packet capture feature. If [the VoIP system is] accessible, you can log in, turn it on, capture traffic, download PCAPs ... and with Wireshark, you can eavesdrop on organizations," Sutton says.

Sutton plans to release a free, new tool he developed to help organizations scan for these types of vulnerable devices in their networks. Called BREWS, it's basically a Web-based and automated version of the scripts he wrote to scan for server headers.

He doesn't consider Google-hacking an easy or effective way to find embedded servers. Scanning for headers is a better approach, he says. "It worked really well because in hardware, headers are unique for a lot of these devices. The Canon photocopier has a return header with 'canon' in it," he says. "Embedded Web servers have different data than a standard Web server: They are very static and tend not to change. There are handful of server headers for HP printers and scanners," for instance, he says.

"The BREWS tool that I'm going to release ... automates what I did so you can scan your own network for embedded Web servers you were not aware of," Sutton says.

The tool also is aimed at gathering and compiling global fingerprint data on these embedded Web devices, he says. "We don't have good information to find these devices. Typically, security scanners focus on Web application servers, not on these" embedded ones, he says.

"We want to encourage people to scan their own networks ... and then it's submitted back to a centralized database, and we'll share the fingerprinting data," he says. Fingerprinting those devices has been difficult because many sit on LANs and can't be scanned externally, he says.

The risk of vulnerable embedded systems has been studied before, including HD Moore's research on VxWorks, the operating system found in many embedded systems. Moore, chief security officer at Rapid7 and chief architect of Metasploit, last year at Defcon and Security BSides showed how he had found hundreds of products connected to the Net that contain a diagnostics service or feature from VxWorks that leaves them susceptible to getting hacked. These devices include VoIP equipment and switches, DSL concentrators, industrial automation systems for SCADA environments, and Fibre Channel switches.

Those, too, were the result of a misconfiguration, but by the developers who used VxWorks. The diagnostics service for developers can be abused by an attacker if left either purposely or inadvertently active in the software. "The service allows access to read memory, write memory, and even power cycle the device. Combined, that is enough to steal data, backdoor the running firmware image, and otherwise take control over the device," Moore said in an interview on the research last year. "This feature shouldn't be enabled" in production mode, but instead deactivated, he says.

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