Cisco Talos previously published research into a targeted attack that leveraged an interesting infection process using DNS TXT records to create a bidirectional command and control (C2) channel. Using this channel, the attackers were able to directly interact with the Windows Command Processor using the contents of DNS TXT record queries and the associated responses generated on the attacker-controlled DNS server.
We have since observed additional attacks leveraging this type of malware attempting to infect several target organizations. These attacks began with a targeted spear phishing email to initiate the malware infections and also leveraged compromised U.S. state government servers to host malicious code used in later stages of the malware infection chain. The spear phishing emails were spoofed to make them appear as if they were sent by the Securities and Exchange Commission (SEC) in an attempt to add a level of legitimacy and convince users to open them. The organizations targeted in this latest malware campaign were similar to those targeted during previous DNSMessenger campaigns. These attacks were highly targeted in nature, the use of obfuscation as well as the presence of a complex multi-stage infection process indicates that this is a sophisticated and highly motivated threat actor that is continuing to operate.