A gang of cybercriminals known for breaking into computer systems and selling access to them has been discovered exploiting an Apache Log4j vulnerability, Log4Shell, in unpatched VMware Horizon to plant cryptominers and backdoors on targeted systems.
In a blog published Wednesday, Blackberry’ researchers Ryan Gibson, Codi Starks and Will Ikard revealed that Prophet Spider was behind the attacks, which could be reliably detected by monitoring ws_TomcatService.exe, the Tomcat service used by VMware Horizon.
The researchers explained that after exploiting the Log4Shell vulnerability to penetrate a system, the attackers use PowerShell commands to download a second-stage payload. In the case of Prophet Spider, the payloads were primarily cryptocurrency mining software, although in some instances, Cobalt Strike beacons—a kind of system backdoor—were also installed on the computers.