Talos recently spotted a targeted phishing attack with several unique characteristics that are not normally seen. While we monitor phishing campaigns used to distribute threats such as Dridex, Upatre, and Cryptowall, targeted phishing attacks are more convincing because the format of the message is personalized to the targeted user. This targeted attack was more difficult to detect because adversaries chose to leverage AutoIT, a well known freeware administration tool for automating system management in corporate environments. This notable characteristic made this attack worthy of further analysis.
Utilizing AutoIT within a payload is unique because it is a legitimate management tool. In this attack, AutoIT was utilized to install a Remote Access Trojan (RAT) and maintain persistence on the host in a manner that's similar to normal administration activity. RATs allow adversaries to fully control compromised hosts remotely to conduct malicious operations, such as exfiltrating sensitive information. The use of AutoIT is potentially an extremely effective method of evading detection by traditional anti-virus technologies and remaining hidden on the system if it is used by the target to manage systems. The combination of a legitimate administration tool being used to install a back-door onto a target system is unique and is why this attack caught our attention.
Another characteristic of this attack that was notable is how adversaries went to great lengths to spoof a phishing message that would appear credible to the user. In this attack, an actual business was impersonated, using the logo and physical address of the business, in order to appear legitimate. The bait in this case is a Microsoft Word document containing a macro that downloads and executes a binary from hxxp://frontlinegulf[.]com/tmp/adobefile.exe.
|Figure 1: A screenshot of the Word document, demonstrating how adversaries impersonated a real company to trick the target.|