Microsoft Reveals Tarrask Malware Threat to Windows Computers

Microsoft’s digital security team is shining the spotlight on Tarrask malware. The new malware from China targets computers that run Windows operating systems. It is believed that the Hafnium hacking collective backed by China is either partially or fully responsible for the malware.  

Which Businesses Have Been hit by Tarrask Malware?

The entities targeted by Tarrask malware include those in the data services, internet service, and telecommunication industries. However, the names of specific businesses affected by the malware have not been publicized.

When Did the Attacks Begin?

The attacks zeroed in on the sectors noted above, starting in the summer of 2021. The attack gradually evolved into the exploitation of zero-day weaknesses within Microsoft Exchange Servers.  

How Does the Tarrask Attack Work?

According to the Microsoft Threat Intelligence Center, often referred to with the acronym of MSTIC, Tarrask is evasion malware, meaning it is designed to evade digital defenses. The malware generates concealed scheduled tasks that wreak havoc on target systems. The abuse of scheduled tasks is actually quite the common means of attempting to evade digital defenses and persistently attacking a targeted system.  

What is Known About the Hafnium Hacking Collective?

Hafnium is best noted for its attacks on Exchange Servers. The Hafnium hacking collective uses zero-day flaws that are not patched correctly in the form of vectors to drop malware and additional web shells and the Tarrask attack. The result is the generation of unique keys within the registry in the Tasks and Tree paths after generating newly scheduled tasks.

Hafnium’s unique approach to implementing malware ultimately leads to the deletion of an important “value” in the targeted computer’s Tree path registry. The value in question is referred to as the Security Descriptor, also referred to with the abbreviation of SD. The Security Descriptor is particularly important in the context of computer security as it defines each of the individual access controls responsible for the activation and running of scheduled tasks.

The Hafnium hacking collective’s successful deletion of the Security Descriptor value within the Tree registry path sets the stage for the task to be concealed from the “schtasks” utility command line as well as the Windows Task Scheduler on the compromised machine. The only way for the user of the targeted computer to know the task is hidden in these spaces is to perform a manual analysis of the computer. Such a manual analysis can be performed by delving deep into the Registry Editor’s paths for a comprehensive examination.

Will Hafnium’s Attacks be Halted?

The way Hafnium executes the Tarrask malware attack is problematic for those who use computers for a living and those who work in the digital security space. The nuances of the attack indicate that Hafnium’s hacking team has a thorough understanding of the subsystems within Microsoft Windows.

The Hafnium hackers use their understanding of the subsystem to conceal activities performed on target endpoints to persistently attack compromised systems without making the target aware that the operating system has been breached. Stay tuned as additional details about Tarrask malware are released to the public in the days and weeks ahead.