A new multistage attack exploiting Elasticsearch servers using the old unpatched vulnerability to invoke a shell with a crafted query and encoded Java commands. The attack aims to deliver BillGates/Setag Backdoor against vulnerable Elasticsearch servers.
The attack targets the already patched vulnerability in the Groovy scripting engine (versions 1.3.0 – 1.3.7 and 1.4.0 – 1.4.2) and the vulnerability can be tracked as CVE-2015-1427 it allows attackers to evade sandbox and to execute arbitrary shell commands via a crafted script.
Security researchers from TrendMicro identified the attack, “the threat actors behind this attack used URL encoding, staged where the scripts are retrieved, and compromised legitimate websites could mean they are just testing their hacking tools or readying their infrastructure before mounting actual attacks.”
Infection Chain – Elasticsearch Servers
The attack starts by searching for a publicly accessible Elasticsearch databases/servers and the attack includes two stages. Once a publicly accessible server is found it “invoke a shell with an attacker-crafted search query with encoded Java commands”.
If the server is vulnerable then the query will get execute successfully and downloads the first-stage script that attempts to stop the firewall running and downloads the second-stage of the payload using curl or wget command.
The second stage of a script similar to the first one attempts to stop firewall and also certain script files that associated with cryptocurrency miners, various config files and other unwanted processes to run its operation.
Also, it removes initial stages of infection, the payloads are likely to be downloaded from the compromised websites to avoid detection.
“A closer look into the binaries revealed a backdoor variant that steals system information and can launch DDoS attacks. The samples bear the hallmarks of the BillGates malware.”
The malware was first spotted in the year 2014 and it is used to launch DDoS attacks, the toolkit includes ICMP flood, TCP flood, UDP flood, SYN flood, HTTP Flood (Layer7) and DNS query-of-reflection flood.
Based on TrendMicro report, “this malware also replaces the affected system’s systools (which enables viewing of system or device information) with a copy of itself, and transfers them to the /usr/bin/dpkgd directory.”
Indicators of Compromise (IoCs):