Russia-linked threat actor TA505 has been observed using a lightweight Office file for malware distribution in a new campaign targeting financial institutions in multiple geographies.
The attacks target organizations across multiple sectors in Canada, the United States, Hong Kong, Europe, and more, and have seen low detection rates in Google’s VirusTotal scanning engine.
Dubbed MirrorBlast, the campaign started in early September, following similar activity in April 2021, Morphisec’s security researchers reveal.
The infection chain starts with a malicious document delivered using phishing emails and later on moves to using the Google feedproxy URL, employing SharePoint and OneDrive lures masquerading as file share requests.
The URLs take the victim to compromised SharePoint or fake OneDrive sites, which help attackers evade detection. Furthermore, a SharePoint sign-in requirement ensures sandboxes are evaded as well.
ActiveX compatibility issues lead to the macro code used in these attacks being executed on 32-bit versions of Office only. The code is responsible for anti-sandboxing checks if the computer name is equal to the user domain and the username is admin or administrator.
Based on the observed TTPs associated with the MirrorBlast campaign, Morphisec believes that the infamous Russia-linked threat actor TA505, also known as Evil Corp, is behind the attacks.
Specifically, the infection chain employs Excel documents leading to the Rebol/KiXtart loader, SharePoint/OneDrive lure themes are employed, and specific domain names are used. Furthermore, a page that one SharePoint lure leads to, along with other artifacts, have already been associated with TA505.
Active since at least 2014, TA505 is a financially motivated adversary best known for the use of the Dridex Trojan and the Locky ransomware. Over the past several years, however, the group has switched to the use of various malware families, including off-the-shelf malware and legitimate tools.
“TA505 is one of many financially motivated threat groups currently active in the marketplace. They are also one of the most creative, as they have a tendency to constantly shift the attacks they leverage to achieve their goals. This new attack chain for MirrorBlast is no exception for TA505 or for other innovative threat groups,” Morphisec notes.
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