McAfee Labs has released new research that reveals a shift in cybercriminals tactics away from external malware threats, towards ‘fileless’ attacks that leverage trusted Windows executables to invade systems and breach corporate networks.
With fileless attacks, threat actors do not install any software on a users computer, making a successful attack extremely hard to detect.
One particular fileless threat, CactusTorch, which can execute custom shellcode on Windows systems, has grown rapidly. It’s evident, according to McAfee Labs, that more and more actors are developing this attack at a significant rate due to the techniques success and ability to evade detection.
CactusTorch uses the NotNetToJScript technique, which loads and executes malicious .NET assemblies straight from memory. These assemblies are the smallest unit of deployment of an application, such as a .dll or .exe. As with other fileless attack techniques, DotNetToJScript does not write any part of the malicious .NET assembly on a computer’s hard drive which means traditional file scanners fail to detect these attacks.
This type of attack abuses trusted .NET libraries exposed over COM, and in this class of attack the malicious .NET Assembly is never written/dropped to disk. The entire process of loading and execution of malicious binary happens in memory at run time. Due to this, the technique bypasses most of the traditional file scanner based detection.
The growth of the ‘fileless’ threat category was also evidenced in McAfee’s recent Q2 Threat report. Many fileless malware campaigns were discovered to leverage Microsoft PowerShell to launch attacks in memory to create a backdoor into a system – surging 432% over 2017.
According to the Ponemon Institute's "The State of Endpoint Security Risk Report," it is estimated that fileless attacks are ten times more likely to succeed than file-based attacks.
Fileless malware takes advantage of the trust factor between security software and genuine, signed Windows applications. Because this type of attack is launched through reputable, trusted executables, these attacks are hard to detect, according to McAfee Labs.