Telecoms, oil and gas companies, media companies and government organizations in India, Malaysia, Singapore, and Vietnam have been receiving spear-phishing emails related to diplomatic discussions in the Asia-Pacific region and containing a specially crafted RTF document.
Once downloaded and opened, the attached document exploits an old Windows common control vulnerability that allows it to drop the Rarstone backdoor and Remote Access Tool (RAT) onto the targeted system unbeknownst to the user, who sees just a decoy document.
"What makes Rarstone unique from PlugX – and other RATs – is its ability to get installer properties from Uninstall Registry Keys. This is so that it knows what applications are installed in the system and how to uninstall them, in the case that these applications inhibit Rarstone’s functions," the researchers shared. "It also uses SSL to encrypt its communication with its C&C server, which not only protects that connection but also making it blend in with normal traffic."
In addition to this, the attackers have also been using dynamic DNS domains and registrars with privacy protection for this campaign, making the researchers' job even more difficult.
The Rarstone backdoor has a remote console, is able to update itself, upload file and data from the target computer, download and execute files on it, and enumerate and terminate processes.