One important task for threat actors is the pursuit of new and innovative techniques for infiltrating their victims’ networks. A major aspect of this pursuit is the selection of a malware that can accomplish the mission at hand. For example, a ransomware threat actor may seek out the ransomware tool that guarantees the highest rate of ransom payment. However, threat actors with different missions might seek out tools using different success criteria. Threat actors can experiment and transition between these tools because, in many ways, these malware varieties represent interchangeable parts in an attack life cycle.
Recent, large-scale distributions of the Zyklon botnet malware mark a continuing trend of off-the-shelf malware use. This multipurpose trojan, capable of supporting numerous criminal activities, has been identified in phishing attacks more and more frequently through the month of April. The bulk of these campaign have leveraged resume- and job-applicant-themed messaging as in the phishing narrative. The most recent analyses of this distribution have shown that the threat actors are attempting to leverage the malware’s full feature set by not only using it as an information stealer, but also as a downloader used to obtain and deploy the Cerber ransomware to infected endpoints. This technique demonstrates threat actor resourcefulness as well as the increasing commodification and democratization of malware utilities once reserved for only the most-technically-capable threat actors.
On 4/6, the Phishing Intelligence team came across a wave of phishing emails that contained a .js file packaged inside of a zip file used to deliver malware. This is nothing new, and has been seen being pushed out by resources associated with the Dridex botnet and the Locky encryption ransomware. The interesting piece is that the attackers are using a new piece of malware called RockLoader to download and install the malware on remote systems. Downloaders are nothing new, as Upatre was used with Dyre and Gameover ZeuS in the past. RockLoader has several tricks up its sleeve.