For the past three months, a cybercrime group has been hacking into home routers –mostly D-Link models– to change DNS server settings and hijack traffic meant for legitimate sites and redirect it to malicious clones.
The attackers operate by using well-known exploits in router firmware to hack into vulnerable devices and make silent changes to the router’s DNS configuration, changes that most users won’t ever notice.
Targeted routers include the following models (the number to the side of each model lists the number of internet-exposed routers, as seen by the BinaryEdge search engine):
D-Link DSL-2640B – 14,327
D-Link DSL-2740R – 379
D-Link DSL-2780B – 0
D-Link DSL-526B – 7
ARG-W4 ADSL routers – 0
DSLink 260E routers – 7
Secutech routers – 17
TOTOLINK routers – 2,265
Troy Mursch, founder and security researcher at internet monitoring firm Bad Packets, said he detected three distinct waves during which hackers have launched attacks to poison routers’ DNS settings –late December 2018, early February 2018, and late March 2018.
Attacks are still ongoing, he said today in a report about these attacks.
How the attacks work
The point of this router hacking campaign was to inject the IP addresses of rogue DNS servers inside people’s routers. Mursch said hackers have used four IP addresses so far.
On these four rogue DNS servers, hackers replaced the IP addresses of legitimate sites with the IP addresses of clone sites they were running.
A normal attack would look like this:
- User’s computer or smartphone receives wrong DNS server settings from the hacked router.
- User tries to access legitimate site.
- User’s device makes a DNS request to the malicious DNS server.
- Rogue server returns an incorrect IP address for the legitimate site.
- User lands on a clone of the legitimate site, where he might be required to log in and share his password with the attackers.
But what legitimate sites the hackers targeted during these three campaigns remains a mystery, for both Mursch and the other security researchers who have looked into these attacks so far.
What researchers did find out was where all this traffic was heading –aka the location of the clone sites.
“The majority of the DNS requests were being redirected to two IPs allocated to a crime-friendly hosting provider (AS206349) and another pointing to a service that monetizes parked domain names (AS395082),” said Mursch, citing another security researcher’s tweet.
DNSChanger attacks have happened before
These types of attacks aren’t new. They have happened before and are usually referred to under the name of “DNSChanger,” after the name of the first malware that started changing DNS settings as a way to redirect users to malicious servers, way back in the 2000s.
DNSChanger incidents are rare in comparison to other types cyber-attacks, but they are extremely dangerous and very efficient, albeit loud and easy to spot for internet-monitoring firms like Bad Packets and others.
Past DNSChanger attacks include a massive malvertising operation that took place in 2016 and during which malicious ads delivered router exploits that changed router DNS settings, and a strain of IoT malware that infected routers in Brazil to change DNS settings to hijack traffic meant for Brazilian banks and redirect it to phishing pages.
But DNSChanger attacks have also happened at the level of nation-state cyber-espionage groups, and not just on the cybercrime scene. The Roaming Mantis cyber-espionage group also hacked routers in a similar fashion and changed DNS settings to redirect users to sites hosting Android malware in early 2018.
As for the attacks detected by Bad Packets, owners of the above listed devices are advised to check their routers’ DNS settings and compare the DNS IP addresses with the ones provided by their internet service provider. A phone call to the ISP’s call center may be needed to get the IP addresses of the ISP’s normal DNS servers.
However, if you see any of the following four IP addresses, then your router’s DNS settings have already been compromised by this campaign, and users need to upgrade their router’s firmware as soon as possible.
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