Ransomware in itself poses a formidable threat for organizations. As a fileless threat, the risk is increased as it can more effectively evade detection. We discuss how Netwalker ransomware is deployed filelessly through reflective DLL injection.Read More
We found a new modular fileless botnet malware, which we named “Novter,” (also reported and known as “Nodersok” and “Divergent”) that the KovCoreG campaign has been distributing since March. We’ve been actively monitoring this threat since its emergence and early development, and saw it being frequently updated. KovCoreG, active since 2011, is a long-running campaign known for using the Kovter botnet malware, which was distributed mainly through malvertisements and exploit kits. Kovter has been involved in click fraud operations since 2015, using fraudulent ads that have reportedly cost businesses more than US$29 million. The botnet was taken down at the end of 2018 through concerted efforts by law enforcement and cybersecurity experts, including Trend Micro.Read More
This new iteration of Purple Fox that we came across, also being delivered by Rig, has a few new tricks up its sleeve. It retains its rootkit component by abusing publicly available code. It now also eschews its use of NSIS in favor of abusing PowerShell, making Purple Fox capable of fileless infection. It also incorporated additional exploits to its infection chain, most likely as a foolproof mechanism to ensure that it can still infect the system. Purple Fox is a downloader malware; besides retrieving and executing cryptocurrency-mining threats, it can also deliver other kinds of malware.Read More
Abusing PowerShell to deliver malware isn’t new; it’s actually a prevalent technique that many fileless threats use. We regularly encounter these kinds of threats, and Trend Micro behavior monitoring technology proactively detects and blocks them. We have smart patterns, for instance, that actively detect scheduled tasks created by malicious PowerShell scripts. We also have network rules that detect, for example, indications of activities like Server Message Block (SMB) vulnerabilities being exploited, potential brute-force attempts, and illicit cryptocurrency mining-related communications.
With that said, a sudden spike of these activities is unusual to us. Feedback from our Smart Protection Network™ revealed that this recent wave of attacks were mostly targeting China-based systems. The attacks, which are still ongoing, were first observed on May 17; the attacks peaked on May 22 and has since steadied.Read More
In some of the recent Powload-related incidents we saw, we noticed significant changes to some of the attachments in the spam emails: the use of steganography and targeting of specific countries. Figure 2 shows the difference. For example, the samples we analyzed in early 2018 had more straightforward infection chains. These updates added another stage to the execution of malicious routines as a way to evade detection.
The Powload variants that use these techniques drop and execute the Ursnif and Bebloh data stealers. We did not see any notable differences in the payloads’ routines. The distribution tactics also resemble a spam campaign we uncovered last year, which delivered the same information stealers but distributed via the Cutwail botnet.Read More