By Edmund Brumaghin, with contributions from Alex Karkins. Ongoing malware distribution campaigns are using ISO disk images to deliver AsyncRAT, LimeRAT and other commodity malware to victims. The infections leverage process injection to evade detection by endpoint security software. These campaigns appear to be linked to a new version of the 3LOSH crypter, previously covered here.
Malware distributors often leverage tools to obfuscate their binary payloads and make detection and analysis more difficult. These tools often combine functionality normally associated with packers and crypters and, in many cases, are not directly tied to the malware payload itself. Over the past several months we have observed a series of campaigns that leverage a new version of one of these tools, referred to as 3LOSH crypter. The threat actor(s) behind these campaigns have been using 3LOSH to generate the obfuscated code responsible for the initial infection process. Based on analysis of the embedded configuration stored within the samples associated with these campaigns, we have identified that the same operator is likely distributing a variety of commodity RATs, such as AsyncRAT and LimeRAT. These RATs feature various functionality that enables them to be used to gain access