Some 2,000 Docker hosts have been attacked and infected by a relatively basic worm that exploits misconfigured permissions to download and run cryptojacking software as malicious containers.
Network security firm Palo Alto Networks in a report today said that despite its "inept" programming, the so-called Graboid worm has been successful: it searches for unsecured docker daemons, uses the access to the Docker host to install malicious images from the Docker Hub, and then runs scripts downloaded from a command-and-control (C2) server. Among the scripts are a cryptomining program that "mines" — or attempts to generate — the Monero cryptocurrency. Each miner is active about 63% of the time, according to Palo Alto.
The worm is not exploiting a vulnerability, but a lack of proper security settings, says Jen Miller-Osborn, deputy director of Palo Alto Networks' Unit 42 threat intelligence group.
"The issues is a lack of updating any of the initial security settings," she says. "The initial point of entry into the Docker host is there because none of the settings were changed. The front door is basically open on these systems."
Cryptomining and cryptojacking have become favored tactics of online attackers as a way of easily monetizing compromised systems, and continues to be used even as the price of cryptocurrencies have declined from their highs of December 2017 and January 2018. Cryptomining through malware and cryptojacking, where resources are used without the owner's authorization, are often used as way to generate a small amount of money from systems that would otherwise not be valuable to attackers.
"While this cryptojacking worm doesn't involve sophisticated tactics, techniques, or procedures, the worm can periodically pull new scripts from the C2s, so it can easily repurpose itself to ransomware or any malware to fully compromise the hosts down the line and shouldn’t be ignored," the company stated in the report.
The worm spreads by identifying vulnerable docker hosts and then sending a command to download a malicious docker image. The image is instantiated as a container, connects to the command-and-control (C2) server and download four scripts that downloads a list of IP addresses of more than 2,000 vulnerable hosts, determines the number of CPUs, and continues to spread.
More than half of the vulnerable hosts are based in China, while about 14% are based in the United States and Ireland accounts for 4%, Palo Alto stated in its analysis.
Palo Alto conducted a simulation of the worm and, assuming that 70% of hosts are available at any given time, found out that it would take less than an hour to infect 1,400 vulnerable hosts. The cluster of 1,400 compromised hosts would give the group approximately 900 CPUs of processing power for cryptomining activities.
Locking Down Containers
Companies need to make sure that they lock down their container-based infrastructure, and know what parts of the infrastructure are their responsibility to secure, Miller-Osborn says.
"With everyone wanting to shift into the cloud, there is a lack of understanding on both the consumer and the provider side of who's responsible for which part of the infrastructure," she says. "These containers that [the worm is] getting into are those that are left open to the entire Internet. It's not something that most people would do on purpose, but whenever they set that up, they fail to implement best practices to secure the images."
The Docker team worked with Palo Alto Networks to remove the malicious images from the Docker Hub.
Palo Alto urged companies to lock down their containers and Docker hosts. Users should connect to the docker daemon with SSH, never use Docker images from unknown repositories or maintainers, and use firewall rules to limit the IP addresses that can access the Docker host.
"Never expose a docker daemon to the internet without a proper authentication mechanism," the company said in the report. "Note that by default the Docker Engine (CE) is NOT exposed to the internet."
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