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Backdoored Business Routers An Emerging Threat

In a troubling new development, threat actors looking for different ways to break into and remain undetected on enterprise networks appear to have begun targeting routers connecting businesses to the Internet.

Once considered a largely theoretical risk, backdoored business routers could soon pose a big problem for enterprises, security vendor FireEye warned in a report released Tuesday.

FireEye said it has discovered at least 14 instances worldwide where attackers have managed to successfully replace the firmware on Cisco business routers with a malicious implant dubbed SYNful Knock by the security vendor.

The implant is basically a clandestine modification of the router’s lOS image and allows attackers to maintain persistence on a compromised system even through reboots, FireEye said. The vendor described the implant as fully modular and customizable in design and capable of being remotely updated after installation.

The implant gives attackers a way to load different modules and executable files on the compromised router and provides attackers with unrestricted access to the system via a backdoor password.

The backdoor is extremely hard to detect on the compromised Cisco routers. It gives attackers a way to not only maintain persistence but also a way to compromise other systems and data on the network to which the router is connected, FireEye said.

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