Android Trojan Switcher Infects Routers via DNS Hijacking
A new Android Trojan uses a victims’ devices to infect WiFi routers and funnel any users of the network to malicious sites. The malware doesn’t target users directly – instead its goal is to facilitate further attacks by turning victims into accomplices.
Researchers at Kaspersky Lab, who discovered the malware and dubbed it Switcher Trojan, claim they’ve seen two versions of the malware. Attackers have used both iterations to commandeer 1,280 wireless networks, most of them in China, according to Nikita Buchka, a mobile security expert with the firm.
One version of the malware mimics a mobile client for the Chinese search engine Baidu. Another passes itself off as a version of an app used for locating and sharing WiFi login information. Once a victim has downloaded one of the versions, it gets to work attacking the router.
The malware does so by carrying out a brute-force password guessing attack on the router’s admin web interface. Once in, Switcher swaps out the addresses of the router’s DNS servers for a rogue server controlled by the attackers along with a second DNS, in case the rogue one goes down.
This makes it so queries from devices on the network are re-routed to the servers of the attacker, something that can open victims to redirection, phishing, malware and adware attacks.
“The ability of the Switcher Trojan to hijack [DNS] gives the attackers almost complete control over network activity which uses the name-resolving system, such as internet traffic,” Kaspersky Lab said Wednesday, “The approach works because wireless routers generally reconfigure the DNS settings of all devices on the network to their own – thereby forcing everyone to use the same rogue DNS.”
The creators of the Trojan were a little sloppy when it came to crafting parts of its command and control website however; they left a table complete with internal infection statistics publicly viewable. According to Buchka, who has reviewed the site, the attackers boast to have infiltrated 1,280 WiFi networks over the last several weeks.
In a Securelist post on the malware posted Wednesday Buchka cautioned users to review their routers’ DNS settings for the following rogue servers: 18.104.22.168, 22.214.171.124, and 126.96.36.199. He also took the opportunity to encourage users – although for many it goes without saying – to verify that they’ve changed their routers’ default login and passwords.
Several weeks ago a handful of router users in Germany fell victim when a variant of Mirai, the nasty malware that’s become synonymous with internet of things vulnerabilities, took hold of their devices. While those routers didn’t suffer from a hardcoded username/password vulnerability, they did have port 7547, usually used by internet service providers to remotely manage the device, open.
The behavior of Switcher is somewhat similar to that of DNSChanger, malware that’s been repurposed as an exploit kit as of late. A recent campaign observed by Proofpoint was targeting wireless routers and changing DNS entries in order to steal traffic. In that instance routers made by D-Link, Netgear, Pirelli and Comtrend were vulnerable. According to Buchka, the hardcoded names of input fields and the structures of the HTML documents that the Switcher Trojan tries to access suggests it may work only on web interfaces of TP-LINK Wi-Fi routers.