A security researcher has come across a campaign in which malicious actors are changing the DNS settings of routers in order to take control of their owners’ Internet connections.
The French researcher known as “Kafeine” first spotted this pharming operation in April. The attackers had been using an exploit kit to hijack small office and home (SOHO) routers through cross-site request forgery (CSRF) attacks. The goal was to change the router’s DNS settings in an effort to redirect users to arbitrary domains. Kafeine noted that the attack only seems to work against Chrome users.
Proofpoint-owned IDS/IPS ruleset and malware intelligence provider Emerging Threats has dubbed this exploit kit DNSChanger EK.
Initially, Kafeine didn’t pay too much attention to the campaign, but in May he noticed that the cybercrooks had made several improvements. After analyzing the traffic associated with the operation, the researcher determined that hundreds of thousands of users from across the world were directed each day to the router exploit kit. On May 9, nearly one million unique connections were recorded.
A large part of the traffic observed on May 16 originated from the United States, Australia, Turkey, Russia, Brazil, India, Argentina, Morocco and Italy.
Kafeine’s analysis has revealed that the cybercrminals are targeting a total of 55 router models from vendors such as ASUS, Belkin, D-Link, Edimax, Linksys, Medialink, Microsoft, Netgear, Netis, Tenda, TRENDnet, and ZyXEL.
DNSChanger EK is designed to fingerprint the targeted device using a modified version of DetectRTC, a small JavaScript library that detects real-time communication (RTC) features such as speakers, microphone, webcam, and audio/video devices. Then, depending on the model of the router, a vulnerability is exploited in order to access the device and change its DNS settings.
The list of exploits spotted by the expert includes CVE-2015-1187, a recently discovered vulnerability that affects D-Link and TRENDnet routers, CVE-2013-2645, which impacts TP-Link devices, and CVE-2008-1244, an old bug that plagues the firmware of Belkin routers. Kafeine believes that even the vulnerabilities for which patches were made available years ago can still plague many routers considering that the firmware is not updated automatically on such devices.
The attackers have changed their DNS servers several times. The researcher spotted the following IPs during his analysis: 217.12.202.93 (most recent), 185.82.216.86 and 37.139.50.45. The server hosted at 217.12.202.93 is no longer active, which indicates that the cybercriminals have likely changed the server once again, Kafeine told SecurityWeek.
The expert noted that while these IPs have been set as the primary DNS, Google’s DNS servers have been used as the secondary DNS to ensure that victims don’t become suspicious in case the attackers’ server becomes unavailable.
Changing the DNS settings on a router allows malicious actors to launch man-in-the-middle (MitM) attacks, seamlessly redirect users to phishing websites, and conduct ad fraud. Based on the analysis of some domains tied to the DNS servers used in the campaign, Kafeine believes the attackers’ goal in this case is likely ad fraud.
In ad fraud schemes, cybercrooks make a profit by replacing the advertisements on the websites visited by users with their own ads.