Threat actors are actively leveraging Amazon and Microsoft public cloud services into their malicious campaigns in order to deliver commodity remote access trojans (RATs) such as Nanocore, Netwire, and AsyncRAT to drain sensitive information from compromised systems. The spear-phishing assaults, which began in October 2021, largely targeted companies in the United States, Canada, Italy, and Singapore, according to Cisco Talos researchers.
These Remote Administration Tools (RATs) versions are loaded with features that allow them to take control of the victim's environment, execute arbitrary instructions remotely, and steal the victim's information.
A phishing email with a malicious ZIP attachment serves as the initial infection vector. These ZIP archive files include an ISO image that contains a malicious loader in the form of JavaScript, a Windows batch file, or a Visual Basic script. When the initial script is run on the victim's machine, it connects to a download server to obtain the next step, which can be hosted on an Azure Cloud-based Windows server or an AWS EC2 instance.
Using existing legitimate infrastructure to assist intrusions is increasingly becoming part of an attacker's playbook since it eliminates the need for the attacker to host their own servers and may also be used as a cloaking strategy to avoid detection by security solutions.
Collaboration and communication applications such as Discord, Slack, and Telegram have found a home in many infection chains in recent months to hijack and exfiltrate data from victim machines. Cloud platform abuse is a tactical extension that attackers may utilize as the first step into a large array of networks.
"There are several interesting aspects to this particular campaign, and it points to some of the things we commonly see used and abused by malicious actors," said Nick Biasini, head of outreach at Cisco Talos. "From the use of cloud infrastructure to host malware to the abuse of dynamic DNS for command-and-control (C2) activities. Additionally, the layers of obfuscation point to the current state of criminal cyber activities, where it takes lots of analysis to get down to the final payload and intentions of the attack."
The use of DuckDNS, a free dynamic DNS service, to generate malicious subdomains to deliver malware is also noteworthy, with some of the actor-controlled malicious subdomains resolving to the download server on Azure Cloud while other servers function as C2 for the RAT payloads.
"Malicious actors are opportunistic and will always be looking for new and inventive ways to both host malware and infect victims. The abuse of platforms such as Slack and Discord as well as the related cloud abuse are part of this pattern," Biasini concluded.
