Newly Discovered Android Trojan Hijacks Routers

The most common way for threat actors to compromise a network router is to attack it directly. The other and potentially more scalable way is to try and get individual users to unwittingly do it for them.

Security researchers at Kaspersky Lab have discovered a dangerous new Trojan dubbed Switcher that is designed to infect and hijack WiFi routers via compromised Android end user devices.

The malware masquerades as two legitimate Android apps—an Android client for Chinese search engine Baidu and a fake version of a Chinese application for sharing WiFi network information.

If a user downloads either app on their Android device and then connects to a WiFi network, the malware tries to gain administrative access to the router by brute-forcing its way in using a predefined list of login combinations

Once it gains access to the router, its switches out the router’s existing DNS server with a malicious one controlled by the attackers. The malware also sets up a secondary DNS server as a failsafe measure in case the primary rogue server is taken down.

By changing a router’s DNS settings, attackers have the ability to redirect traffic from all devices connecting to the router to websites controlled by the attackers, thereby exposing the victims to phishing, adware, malware and other threats, Kaspersky Lab security researcher Nikita Buckha wrote in a blog post.

The malware authors have created a website to promote and distribute the two malicious WiFi apps. The server hosting the website also doubles as the command and control server for the malware. An analysis of the server shows that the attackers have managed to compromise at last 1,280 Wi-Fi networks so far, Buchka said.

“The Switcher Trojan marks a dangerous new trend in attacks on connected devices and networks,” he said. “It does not attack users directly. Instead, it turns them into unwilling accomplices: physically moving sources of infection.”

What makes Switcher so dangerous is the fact that it targets the entire network and not just individual users.

The DNS changes that Switcher makes are hard to detect and can survive a router reboot, Buckha said. And because a secondary DNS server is available, Switcher can continue to redirect traffic from all devices connecting to a compromised network via the secondary, failsafe DNS server.

“For example, the attackers are able to redirect user’s requests to popular sites such as Facebook and Twitter, to perform some phishing activities [or] ask for login and passwords to access user accounts,” Buchka told Dark Reading.

“In addition, attackers can just redirect all user requests to web pages that contains a bunch of advertisements, thus generating profit," he says.

And importantly, Switcher gives cybercriminals the ability to infect devices connected with infected WiFi with other malware, he says.

Individual users are not the only ones impacted by Switcher. Businesses have reason for concern as well, according to Buckha. “In fact, it is more likely that public WiFi hotspots in some restaurant or cafe will be attacked by Switcher, simply because more people are connecting to them,” he says.

Switcher is the first Android malware sample to target routers in this manner. But for the moment at least, the threat appears confined to Chinese users, Buchka adds.

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