New Service Detects Backdoors in Software

Here's something else to keep you up at night: Most of today's scanning tools can't detect software backdoor programs that can be inserted during the development process.

Researchers at Veracode have identified several different forms of these backdoor programs, which are sometimes inserted purposely by the developer for debugging reasons and can inadvertently put the app at risk -- as well as those that can be easily sneaked into applications by malicious coders or attackers.

Fortify Software researchers dub the malicious form of this threat as "cross-build injection" -- where vulnerabilities and malware such as backdoors are tucked into code during the software development process. (See Hackers Attack Apps While Still in Development and Another 'Cross' to Bear.)

Veracode today also announced that it has added new features to its SecurityReview application security scanning service that detect some of these backdoor programs, which can sit quietly and invisibly in an application without your knowledge, leaving the door unlocked for an attacker to take over your machines.

"People doing manual code review look for vulnerabilities, but not typically for backdoors," says Chris Wysopal, CTO and co-founder of Veracode. "We built a metal detector for this."

Wysopal says several of Veracode's financial services customers had approached the company with concerns about this potential threat in the third-party software products they purchase and that their developers write. "They said: 'I'd like to have a solution for finding backdoors... I know I can't 100 percent trust my own developers to find them.'"

But it's not just the financial industry that may be at risk. In a recent report by the Defense Science Board on the risks of the Department of Defense's dependence on software manufactured outside of the U.S., the DSB discusses the need for assuring the software purchased by the DOD isn't sabotaged in any way. (The DSB is a federal advisory committee to the DOD.)

"The low-hanging fruit to exploit the DOD's infrastructure is switching from finding a vulnerability in software and exploiting it... to what if someone subverts the development team in the software supply chain and puts in malicious code we don't know about," Veracode's Wysopal says.

Wysopal says a researcher at a recent Department of Homeland Security software assurance conference spoke about a study he did on downloaded software risks. He found that 23 software packages that government employees might download for tools or for developing apps for their agencies, had backdoors within them. "That's a startlingly high number," Wysopal says. "The only solution has been to read through the source code and do a manual code review. Static analysis tools don't scan for backdoors."

Veracode's new scanning features are based on its static binary-analysis technology, and is at no extra charge for Veracode's customers. The service now scans for special credential backdoors, hidden functionality backdoors, and rootkits. Special credential backdoors are when a developer or attacker hard-codes passwords or keys into the program code, including username and password, for instance. Developers sometimes do so for debugging or customer support, but if this code is found or known by an attacker, it's the key to the kingdom.

Hidden functionality backdoors are special commands inserted into the code that lets an attacker issue commands or authenticate without going through the app's standard application procedure. This is becoming a popular feature on Web-based platforms, according to Veracode's research.

One third of the backdoors Veracode detected in its research were inserted by the developer rather than attackers. Still, that's a dangerous practice, Wysopal says: "I don't care if a feature was put in on purpose by the developer for debugging, or maliciously by an attacker. In both cases, the threat is equivalent."

Rootkit backdoors, meanwhile, are programs aimed at hiding activity on a system from the system administrator. "The big tell-tale sign of a rootkit is the software is doing something it's not supposed to do," Wyospal says.

Wysopal says Veracode hasn't seen any major exploits using these backdoor programs as yet. "But it's hard to understand why you would put in a backdoor unless you intended to use it at some point," he says. And the danger is that the software will appear to be behaving and functioning normally: "No IDS is going to go off. It's extremely hard to detect when there's a backdoor."

Next for Veracode: scanning for backdoors that perform what it calls unintended network activity as well as ones that manipulate security parameters, such as user privileges.

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