The threat group known as TA505 (aka Hive0065) is known for conducting large-scale phishing campaigns but has not been active since 2020. Now phishing campaigns have been detected that indicate the threat group is conducting attacks once again, with the first mass-phishing campaigns by the group detected in September 2021.
The initial campaigns were small and consisted of a few thousand phishing emails, but as the month progressed larger and larger campaigns were conducted, with phishing campaigns conducted by the group now consisting of tens of thousands of messages. The geographic range has also been increased beyond North American where the gang was initially concentrating its attacks.
Social engineering techniques are used to convince victims to open email attachments or visit links and view shared files, with a variety of lures used by the gang in its phishing attacks. Emails intercepted from the latest campaigns claim to provide insurance claims paperwork, situation reports, media release requests, health claims, and legal requests. Many of the campaigns so far have targeted employees in financial services.
One of the hallmarks of the group is using Excel file attachments in emails that contain malicious macros which deliver a Remote Access Trojan (RAT), the downloading and execution of which gives the group control over victims’ devices. The group is also known to use HTML files that link to malicious websites where the malicious Excel files are downloaded.
While the attacks often start with a file attachment, later in the attack process a Google feedproxy URL is used with a SharePoint and OneDrive lure that appears to be a file share request, which delivers the weaponized Excel file.
The initial infection stage involves the downloading of a Microsoft installer package, which delivers either a KiXtart or REBOL malware loader, which pulls a different MSI package from the C2 server, which then installs and executes the malware. TA505 is known to use the FlawedGrace RAT, which first appeared in 2017, and the latest campaign delivers a new variant of this malware using a malware loader dubbed MirrorBlast. According to an analysis of MirrorBlast by Morphisec labs, the malware will only run in 32-bit versions of Microsoft Office as there are compatibility issues with ActiveX objects.
Macros are disabled by default in Microsoft Excel as a security measure, so social engineering techniques are used in the attacks to convince victims to enable macros. Macros are more commonly used in Excel files than Word files, and end users may not be as suspicious of Excel macros as Word macros.
Email security solutions are capable of detecting files containing Excel macros, especially email security solutions with sandboxing. In an attempt to bypass those measures and ensure the emails are delivered, TA505 uses lightweight, legacy Excel 4.0 XLM macros rather than the newer VBA macros, which has seen many of the messages bypass email security gateways.
TA505 is a highly creative threat group that regularly changes its attack techniques to achieve its goals, with the gang known to have conducted campaigns to deliver the Dridex banking Trojan, Locky and Jaff ransomware, and the Trick banking Trojan.
The group is known for conducting high-volume phishing campaigns that have targeted a range of different industry sectors and geographical areas.
TA505’s tactics, techniques, and procedures are expected to continue to evolve so it is vital for organizations to ensure email security defenses are implemented to block the emails. Security awareness training should also be provided to the workforce and employees should be made aware of the latest tricks and tactics used by the gang, including raising awareness of the use of Excel files with macros in phishing emails.