Experts at TrendMicro discovered that routers manufactured by Chinese security vendor and sold under the brand name Netcore in China have a hard-coded password. The hard-coded password allows attackers to access user’s traffic with a backdoor, the Netcore routers are also sold in other countries, including South Korea, Taiwan, Israel and United States, under the brand Netis.
As explained in the blog post published by Tim Yeh, Threat Researcher at Trend Micro, bad actors could exploit the backdoor to bypass router security and to run malicious code on device or change settings.
“This backdoor is “protected” by a single, hardcoded password located in the router’s firmware. Netcore/Netis routers appear to all have the same password. This “protection” is essentially ineffective, as attackers can easily log into these routers and users cannot modify or disable this backdoor. Almost all Netcore/Netis routers appear to have this vulnerability, based on the information we examined.”states the post.
The backdoor discovered by experts is an open UDP port, accessible from the WAN side of the router, listening at port 53413. The presence of the backdoor allows attackers to compromise the Netcore router if it is accessible from the Internet just knowing the password hardcoded into the firmware. This attack scenario is common for almost all residential and SMB users, exploiting the backdoor the threat actors could upload or download malicious code, change device settings, run a man-in-the-middle (MitM) attack to eavesdrop the user’s internet communication and steal sensitive information.
In the following image is reported the output Netstat tool which reports the Local addressed for the web admin and backdoor ports.
Netcore – Netis routers are known for providing the best wireless transfer speed up to 300Mbps, offering a better performance on online gaming, video streaming, and VoIP phone calling.
An additional element of concern it that Netcor – Netis routers have all the same password and the backdoor cannot be changed or disable. The security issue has an impact on millions of devices worldwide, this is the number of routers discovered online with a large scale scanning. It is quite easy to discover vulnerable Netcore – Netis routers with an ordinary port scan searching for the above UDP port open.
“Using ZMap to scan vulnerable routers, we found more than two million IP addresses with the open UDP port,” “Almost all of these routers are in China, with much smaller numbers in other countries, including but not limited to South Korea, Taiwan, Israel, and the United States.” Yeh wrote in the post.
Experts at Trend Micro also discovered that a configuration file containing the credentials for the web-based administration panel on the router is stored in clear text and for accessible to attackers.
The post closes with a bad news for Netcore – Netis owners as explained by Yeh:
“Users have relatively few solutions available to remedy this issue. Support for Netcore routers by open source firmware like dd-wrt and Tomato is essentially limited; only one router appears to have support at all. Aside from that, the only adequate alternative would be to replace these devices,”
(Security Affairs – Netcore – Netis routers, backdoor)