An analysis of the tactics, techniques and procedures used by attackers to exploit a vulnerability in the Elasticsearch enterprise search engine suggests that it takes very little skill these days to develop a large-scale infrastructure for launching distributed denial of service attacks.
That is the assessment of researchers at cyber analytics firm Novetta, based on data gathered from an open-source honeypot named Delilah that the company recently deployed to gain a better understanding of the threat actors exploiting the Elasticsearch flaw.
Most of the attackers exploiting the vulnerability aren’t highly skilled, says Greg Sinclair, director of malware research. Even so, “they have gone out and created a streamlined method for using this vulnerability to create an effective DDoS infrastructure,” he said.
Earlier this year, a security flaw was discovered in Elasticsearch’s Groovy scripting engine that allowed attackers to remotely execute malicious code on vulnerable Elasticearch servers. Following public disclosure of the flaw, researchers reported large-scale scanning and exploitation of the flaw, resulting in a large number of Elasticsearch servers being compromised, Novetta said in a report summarizing the results of its research.
Though the vulnerability was only discovered in February 2015, there are signs that it was being actively exploited by attackers at least since November 2014 and possibly even as early as July last year.
The flaw has been patched, but a large number of Elasticsearch servers remain unpatched and therefore vulnerable to attacks, Sinclair said.
Novetta’s investigation of the flaw via its honeypot project shows that two different malware families, dubbed Elknot and BillGates, are being installed on compromised Elasticsearch servers. Both are DDoS bots and have a shared lineage but vary greatly in sophistication, according to Sinclair.
Elknot appears to be a pretty basic DDoS bot that employs a rudimentary set of commands to generate denial-of-service attacks against specified targets. The BillGates family, on the other hand, features a more robust code base and has the ability to execute different malware programs in addition to functioning as a DDoS bot.
“It is essentially a backdoor into someone’s Elasticsearch server,” Sinclair says. “It is more persistent than Elknot and stays on the machine for longer,” using obfuscation tactics.
The command-and-control servers that are being used by attackers to communicate with compromised Elasticsearch servers contain several other malware families that can be installed just as easily on compromised systems as Elknot and BillGates. Many of the samples hosted on these servers are old exploits that can be used by attackers to move laterally across networks.
The fact that the threat actors exploiting the Elasticsearch flaw have not done that so far suggests that data theft is not a motive, Sinclair says.
“Moreover, the actors appear to have little more than 'script-kiddie' skill levels, as the tools being used by the actors are easily acquired and meant to be deployed practically off the shelf, requiring almost no customization for a victim’s machine, Novetta’s report noted.
Even so, the large-scale scanning and continued targeting of vulnerable Elasticsearch servers shows just how easy it has become for anyone to build a DDoS attack infrastructure, it said.
A majority of the C&C servers used in the Elasticsearch exploitation campaign has addresses within the Chinese IP space. A majority of the DDoS targets were Chinese too, though Novetta observed a fair number of American companies being targeted as well. In total, during Novetta’s observation of honeypot activity, the company saw a total of 384 attack commands being directed at 95 unique IPs in China and 133 DDoS attack commands directed at 133 U.S. based IP addresses. The most commonly used attack commands were SYN Flood, UDP Flood and Ping Flood.