Security researchers from Red Canary discovered potential hacker group Blue Mockingbirddeploying Monero cryptocurrency-mining payloads deployed on the Internet-facing Windows machines at multiple organizations.
The group found to be active since December 2019 and they use several techniques to bypass security technologies.
Blue Mockingbird Campaign
To gain initial access attackers exploit public-facing web applications those specifically using Telerik UI for ASP.NET AJAX.
Telerik UI is a suite of user interface components that helps in the web development process, 2019.3.1023 version affected with deserialization vulnerability(CVE-2019-18935).
This vulnerability found to be exploited by Blue Mockingbird to gain initial access to the system and to escalate privileges they use the JuicyPotato technique.
Once they gain full access to the system they deploy a popular version of Monero-mining tool XMRIG packaged as a DLL.
To maintain persistence the hacker group uses a novel “COR_PROFILER COM hijack to execute a malicious DLL and restore items removed by defenders.”
As the COR_PROFILER method was configured every process that loads the Microsoft .NET Common Language Runtime would establish persistence.
In some cases, the actor even created a new service to perform the same actions as the COR_PROFILER payload, reads Red Canary blog post.
By using the JuicyPotato exploit the hacker group escalates privileges from an IIS Application Pool Identity virtual account to the NT Authority\SYSTEM account.
Blue Mockingbird uses these techniques to move laterally and distribute mining payloads across the enterprise.
Once they escalate the privilege to NT Authority\SYSTEM, attackers use RDP to deploy payload on the remote systems, in some cases the tasks were created remotely.
To mitigate the attacks, it is recommended to patching web servers, web applications, and dependencies of the applications. Red Canary published a detailed report with indicators Indicators of compromise.