Mirai Botnet is Evolving and Now Has a 5th Victim in Germany

The Mirai botnet is alive and hunting another round of targets. This time, it is vulnerable and unsecured IoT devices produced by Zyxel and SpeedPort in Germany. Over Sunday and Monday during this past week, Deutsche Telecom experienced a less than .5% outage of customers (approximately 900,000) due to an upgraded version of the botnet that is leveraging new attack vectors to compromise IoT routers. These attack vectors are significant because it is the first time a real-world attack is leveraging both vulnerabilities and privileges en masse and in an automated botnet fashion. In this blog I will review how this latest Mirai botnet is propagating, how the level of sophistication is actually decreasing, and steps to take to keep it from spreading.

How the Latest Mirai Botnet is Propagating

This new version of Mirai leverages a known Remote Code Execution flaw that operates on port 7547 used by ISPs to manage the devices remotely. If successful, the botnet attempts to log in using three different default passwords and then deploys its payload including closing the offending port to prevent reinfection and remote management to clear the malware. Vulnerable routers then receive exploit code every 5 to 10 minutes per target in order to keep a sustained attack viable.

Key Takeaways: Hardware Reboots Aren’t Enough; Attacks Getting Less Sophisticated

Deutsche Telecom has already released a patch that simply requires a router reboot to download new firmware, but the number of devices still infected and modifications to Mirai demonstrate that a blended attack, using more than one type of device (exploits for MIPS and ARM chipsets), can cause chaos to virtually every system – from DNS provider, to bank, to simple home end user. A second important take away from this latest Mirai attack is the level of sophistication. Actually, the opposite; the attack is not sophisticated at all. The Mirai source code has been public for over a month now, and in the beginning of November Metasploit released a module specifically for this vulnerability. Someone decided to weaponize the exploit module and include it in Mirai to allow for the infection of even more IoT devices. This is more creativity with exploit-style building blocks than it is sophistication in creating a new attack vector, vulnerability and exploit.

Steps to Take

We have seen several Mirai attacks in the last three months, including French Telecom, Krebs on Security, Dyn, Liberia, Russian banks, and now Deutsche Telecom. Stopping these attacks requires action on multiple levels. There are proposed enhancements to current legislation between nations to stop the proliferation of this type of weaponized exploit: The Wassenaar Agreement. While the agreement was designed for weapons of mass destruction, earlier in the year amendments where proposed to stop exploit code from being sold and shared across countries. Unfortunately, this initiative appears to have died on the vine and no updates have been made since early this summer. This implies that governments are not ready to get involved and threats like this will continue to increase until action is taken at the country level to protect the distribution of exploits and the sale of vulnerable IoT devices. Considering this latest attack is using blended vulnerability and privilege attack vectors, all stakeholders need to be aware of the risk. Patching vulnerabilities and changing default passwords is the best way to mitigate these risks since there is no legal way to mitigate the sale of faulty devices, force vendors to keep them secure, and stop the proliferation of exploit code for anyone to weaponize.