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Online criminals—at least some of them wielding the notorious Mirai malware that transforms Internet-of-things devices into powerful denial-of-service cannons—have begun exploiting a critical flaw that may be present in millions of home routers.
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Routers provided to German and Irish ISP customers for Deutsche Telekom and Eircom, respectively, have already been identified as being vulnerable, according to recently published reports from researchers tracking the attacks. The attacks exploit weaknesses found in routers made by Zyxel, Speedport, and possibly other manufacturers. The devices leave Internet port 7547 open to outside connections. The exploits use the opening to send commands based on the TR-069 and related TR-064 protocols, which ISPs use to remotely manage large fleets of hardware. According to this advisory published Monday morning by the SANS Internet Storm Center, honeypot servers posing as vulnerable routers are receiving exploits every five to 10 minutes.
SANS Dean of Research Johannes Ullrich said in Monday’s post that exploits are almost certainly the cause behind an outage that hit Deutsche Telekom customers over the weekend. In a Facebook update, officials with the German ISP said 900,000 customers are vulnerable to the attacks until they are rebooted and receive an emergency patch. Earlier this month, researchers at security firm BadCyber reported that the same one-two port 7547/TR-064 exploit hit the home router of a reader in Poland. They went on to identify D1000 routers supplied by Eircom as also being susceptible and cited this post as support. The Shodan search engine shows that 41 million devices leave port 7547 open, while about five million expose TR-064 services to the outside world.
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The attacks started shortly after researchers published attack code that exploited the exposed TR-064 service. Included as a module for the Metasploit exploitation framework, the attack code opens the port 80 Web interface that enables remote administration. From there, devices that use default or otherwise weak authentication passwords can be remotely commandeered and made to join botnets that carry out Internet-crippling denial-of-service attacks.
BadCyber researchers analyzed one of the malicious payloads that was delivered during the attacks and found it originated from a known Mirai command-and-control server.
“The unusual application of TR-064 commands to execute code on routers has been described for the very first time at the beginning of November, and a few days later a relevant Metasploit module had appeared,” BadCyber researchers wrote in a blog post. “It looks like someone decided to weaponize it and create an Internet worm based on Mirai code.”
All bases covered
To infect as many routers as possible, the exploits deliver three separate exploit files, two tailored to devices running different types of MIPS chips and a third that targets routers with ARM silicon. Just like the Metasploit code, the malicious payloads use the exploit to open the remote administration interface and then attempt to log in using three different default passwords. The attack then closes port 7547 to prevent other criminal enterprises from taking control of the devices.