Diligent hackers have decided routers and cameras aren't enough, and have reportedly crafted Mirai variants targeting Linux servers.

That unwelcome news came from Netscout, whose Matthew Bing wrote: "This is the first time we've seen non-IoT Mirai in the wild."

Bing's post explained that the botmasters are trying to use a Hadoop vulnerability as the vector to spread Mirai. The bug was first published on GitHub eight months ago, and attacked the platform's YARN resource management technology with command injections.

Netscout, Bing wrote, has seen tens of thousands of exploit attempts against Hadoop YARN each day, and among the 225 binaries the attackers are trying to inject into victims' machines "at least a dozen of the samples we've examined are clearly variants of Mirai".

Because the attack is specific to YARN, the Mirai variant Netscout analysed is simpler than its predecessors. Older Mirai versions designed to infect Internet of Things devices had to identify whether the platform they were attacking was x86, x64, Arm, MIPS and so on.

This variant is only interested in x86 machines, Bing wrote.

The "VPNFilter" variant "still tries to brute-force factory default usernames and passwords via telnet", he continued. If any are found, the attacker didn't install malware on the victim, but rather "phoned home" with the target's IP address, username and password.

Last week, Radware's Pascal Geenens warned that Hadoop YARN exploit traffic was running at a very high rate – around 350,000 events per day.

Geenens warned systems are particularly at risk of cryptomining abuse, and added that if a Hadoop system has a publicly exposed YARN service, "it is not a matter of IF but a matter of WHEN your service will be compromised and abused". ®