It's hard to keep a bad bot down. That's just one of the lessons that comes with Wicked Mirai, the latest variation on the Mirai Internet of Things botnet software. In the newest version, multiple payloads are available for delivery in a package that includes at least three new exploits that demonstrate how its developers are continuing to expand its reach.
Researchers at Fortinet recently found this new variation, which they dubbed Wicked Mirai, named for a string within the code that seems to point back to the hacker responsible for the new variant. In looking at the code, they found malware that scans multiple ports on network devices, using open ports to download copies of different payloads depending on which ports are available.
The researchers note that the attack module shows evolution from the original Mirai code. The original relied on brute force attacks, using a theme and variation on "guessing" as a tactic, while the new version relies on a variety of port-related vulnerability exploits, some new and some very old, to gain access to a device.
Once on a system, Wicked Mirai contacts a C&C server from which it downloads a payload. The payload seems to include something from the Sora, Owari, and Omni Mirai variant families — the specific download appears to have shifted between the three during the time that the researchers have been monitoring the server.
"The Mirai botnet variants we have grown accustomed to seeing are typically used as a 'land and expand' exploit kit," says Dean Weber, CTO of Mocana, explaining that the code would hit a system and then pivot to infecting other devices on the network rather than immediately download malware payloads.
Wicked looks for specific vulnerabilities on a platform that the botnet can exploit. The reason for this tactical evolution is simple. "The bottom line is that this allows the botnet controllers to have a faster compromise time, which in the end, allows for the botnet to come online faster," Weber says.
Wicked has also added IoT persistence to its toolkit, making the malware part of the IoT devices it infects beyond the occasional reboot seen in IoT networks. "The ability to achieve this level of persistence, combined with the ease of infection in the first place, is another example of why DDoS attacks continue to be on the rise," says Sean Newman, director of product management at Fortinet.