Vulnerable Docker services are being targeted by a novel campaign in which the threat actors are deploying XMRig cryptocurrency miner as well as the 9Hits Viewer software as part of a multi-pronged monetization strategy.
"This is the first documented case of malware deploying the 9Hits application as a payload," cloud security firm Cado said, adding the development is a sign that adversaries are always on the lookout for diversifying their strategies to make money off compromised hosts.
9Hits advertises itself as a "unique web traffic solution" and an "automatic traffic exchange" that allows members of the service to drive traffic to their sites in exchange for purchasing credits.
This is accomplished by means of a software called 9Hits Viewer, which runs a headless Chrome browser instance to visit websites requested by other members, for which they earn credits to pay for generating traffic to their sites.
The exact method used to spread the malware to vulnerable Docker hosts is currently unclear, but it's suspected to involve the use of search engines like Shodan to scan for prospective targets.
The servers are then breached to deploy two malicious containers via the Docker API and fetch off-the-shelf images from the Docker Hub library for the 9Hits and XMRig software.
"This is a common attack vector for campaigns targeting Docker, where instead of fetching a bespoke image for their purposes they pull a generic image off Dockerhub (which will almost always be accessible) and leverage it for their needs," security researcher Nate Bill said.
The 9Hits container is then used to execute code to generate credits for the attacker by authenticating with 9Hits using their session token and extracting the list of sites to visit.
The threat actors have also configured the scheme to allow visiting adult sites or sites that show popups, but prevent it from visiting cryptocurrency-related sites.
The other container is used to run an XMRig miner that connects to a private mining pool, making it impossible to determine the campaign's scale and profitability.
"The main impact of this campaign on compromised hosts is resource exhaustion, as the XMRig miner will use all available CPU resources it can while 9hits will use a large amount of bandwidth, memory, and what little CPU is left," Bill said.
"The result of this is that legitimate workloads on infected servers will be unable to perform as expected. In addition, the campaign could be updated to leave a remote shell on the system, potentially causing a more serious breach."
