McAfee Labs has noticed a significant shift by some actors toward using trusted Windows executables, rather than external malware, to attack systems. One of the most popular techniques is a “fileless” attack. Because these attacks are launched through reputable executables, they are hard to detect. Both consumers and corporate users can fall victim to this threat. In corporate environments, attackers use this vector to move laterally through the network.
One fileless threat, CactusTorch, uses the DotNetToJScript 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; hence traditional file scanners fail to detect these attacks.
In 2018 we have seen rapid growth in the use of CactusTorch, which can execute custom shellcodeon Windows systems. The following chart shows the rise of CactusTorch variants in the wild.