A new
variant of the Mushtik botnet has been found attacking routers using the open-source
Tomato router firmware with about 4.600 routers currently exposed on the internet.

Musthtik has been operating since March 2018 using a worm-like propagating ability to infect and harvest Linux servers and IoT devices. The good news is the new variant uses its botnet for only a few tasks, cryptocurrency mining as to launch DDoS attacks and it has not been spotted injecting any additional malware onto a system, said Palo Alto Networks Unit 42.

The new
twist implemented by Mushtik’s operators is the use of a new scanner that
searches for Tomato routers on TCP port 8080 and then bypasses the admin web
authentication by default credentials bruteforcing. In most cases these searches
are conducted by devices already under the botnet’s control.

The botnet also
still uses its previous methodology to find new members. That is using its
members to look for vulnerable services such as WordPress, Drupal and Weblogic
to enter a system.

“Botnet
developers are increasingly compromising IoT devices installed with the open
source firmware, which often lack the security updates and maintenance patches
necessary to keep devices safeguarded. End users should be cautious when
installing open source firmware and must follow the security guidelines in the
firmware manual,” Unit 42 said.