Several attacks observed over the past few months that rely heavily on PowerShell, open-source tools, and fileless malware techniques might be the work of a single group of hackers.
An investigation started by security researchers from Morphisec into a recent email phishing attack against high-profile enterprises pointed to a group that uses techniques documented by several security companies in seemingly unconnected reports over the past two months.
"During the course of the investigation, we uncovered a sophisticated fileless attack framework that appears to be connected to various recent, much-discussed attack campaigns," Michael Gorelik, Morphisec's vice president of research and development, said in a blog post. "Based on our findings, a single group of threat actors is responsible for many of the most sophisticated attacks on financial institutions, government organizations, and enterprises over the past few months."
The Morphisec investigation started with a phishing email that distributed a Microsoft Word document with malicious macros inside. When opened, the document asked the victim to click on the "Enable Content" button in order to view the supposedly protected content. Doing so allowed the malicious embedded code to execute.
From that point on, the attack used a succession of scripts written in PowerShell, a powerful scripting engine included in Windows, to set up persistence through registry keys and establish a communication channel with the attacker's server.
The attackers then downloaded and executed various open-source tools that allowed them to perform a deeper investigation of the system, steal locally stored Windows credentials, and open reverse shells to their server.
Some of the observed tools included Mimikatz, Lazagne, and Meterpreter, the payload of the popular Metasploit penetration testing framework. These programs were loaded directly into the computer's memory and left no traces on disk.
In February, researchers from Kaspersky Lab reported a string of stealthy, fileless attacks against more than 100 enterprises, banks, and government organizations from around the world. Those attacks used very similar techniques and tools, including PowerShell, Mimikatz, and Meterpreter.
In the attack investigated by Morphisec, the attackers also used a PowerShell script that established a two-way communication channel using DNS TXT records. A similar script was documented by researchers from Cisco Talos in early March in a PowerShell-based attack that they dubbed DNSMessenger.
The fileless malware techniques and DNS communication method were also described by researchers from FireEye in a March report about attacks targeting employees from various U.S. organizations whose jobs involved Securities and Exchange Commission (SEC) filings. FireEye attributed those attacks to a financially motivated attack group that the company has been tracking for a while under the name FIN7.
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