A recently identified financially motivated threat actor is targeting companies in the United States and Germany with custom malware, including a screenlogger it uses for reconnaissance, Proofpoint reports.
Tracked as TA866, the adversary appears to have started the infection campaign in October 2022, with the activity continuing into January 2023.
As part of the campaign, which Proofpoint refers to as Screentime, victims are targeted with malicious emails containing an attachment or a URL that leads to the deployment of malware. In some cases, based on the attacker’s assessment of the victim, post-exploitation activity may commence.
In October and November 2022, a small number of companies in the US were targeted with emails carrying Publisher file attachments containing malicious macros.
In November and December, the attackers switched to using URLs leading the intended victims to Publisher files containing macros or to JavaScript files. Some of the emails were seen carrying PDF attachments containing URLs to JavaScript files.
After switching to URLs, the attackers also scaled the campaign, sending thousands or tens of thousands of malicious messages several times per week, targeting thousands of organizations. In January 2023, the email volume increased even more, but the frequency of attacks was reduced, Proofpoint says.
Emails observed in January appeared to use thread hijacking with a ‘check my presentation’ lure to trick recipients into clicking the malicious URLs.
The malicious links lead to the 404 TDS (traffic distribution system) that filters the traffic and redirects the victim to a JavaScript file. If the victim runs the file, a MSI package is fetched and executed, which in turn runs an embedded VBS script and achieves persistence.
The script is the WasabiSeed malware, which downloads and executes another MSI file representing a piece of malware named Screenshotter, and then continues polling the URL for additional payloads.
With variants implemented in different programming languages (including Python, AutoIT, and JavaScript/IrfanView), Screenshotter was designed to take screenshots of the victim’s screen and send them to a command-and-control (C&C) server.
According to Proofpoint, the attackers likely manually inspect the screenshots and use WasabiSeed to deploy additional payloads if the victim is deemed interesting, such as the AHK Bot, which too enters a loop to fetch additional components.
AHK Bot has been observed deploying a script to check the victim machine’s Active Directory (AD) domain and downloading and loading in memory the Rhadamanthys information stealer. The AD profiling, Proofpoint notes, could lead to the compromise of other domain-joined hosts.
Proofpoint has been tracking the use of 404 TDS since September and believes that it is either sold or shared between cybercriminals, as it has been used in various phishing and malware campaigns.
As part of TA866’s Screentime campaign, hundreds of random URLs were used, leading to 20 domains that were registered on the day of the attack.
“These domains were previously registered, expired, and then re-sold to the TDS operator,” Proofpoint notes.
Some parts of the observed attacks involve manual interaction from the threat actor and, based on payload download time, Proofpoint’s security researchers believe that TA866 could be residing in the UTC+2 or UCT+3 time zones. These time zones correspond, among others, to Russia.
Furthermore, the researchers discovered that AHK Bot contains Russian language variable names and comments, and that the malware has been used in attacks since at least 2019, with some of the previous activity seemingly having an espionage objective.
“TA866 is a newly identified threat actor that distributes malware via email utilizing both commodity and custom tools. Most of the activity recently observed by Proofpoint suggests recent campaigns are financially motivated, however assessment of historic related activities suggests a possible, additional espionage objective,” Proofpoint concludes.
Related: North Korean Hackers Created 70 Fake Bank, Venture Capital Firm Domains
Related: Vietnam-Based Ducktail Cybercrime Operation Evolving, Expanding
Related: US Government Agencies Warn of Malicious Use of Remote Management Software
