Atrás 
Netskope Threat Labs publishes a monthly summary blog post of the top threats we are tracking on the Netskope platform. The purpose of this post is to provide strategic, actionable intelligence on active threats against enterprise users worldwide.
Summary
- Attackers continue to attempt to fly under the radar by using cloud apps to deliver malware, with 58% of all malware downloads in March originating from 162 cloud apps.
- While malicious PE (EXE/DLL) files, archives (ZIP, 7Z, GZ), and plain text files (PS, LNK) continue to dominate malware downloads, DMG files are on the rise as attackers target Mac OSX users.
- Trojans continue to represent the majority of malware downloads, used to deliver payloads such as the infostealers RecordBreaker and AgentTesla, and the Stop and Royal ransomware.
Cloud Malware Delivery
Attackers attempt to fly under the radar by delivering malicious content via popular cloud apps. Abusing cloud apps for malware delivery enables attackers to evade security controls that rely primarily on domain block lists and URL filtering, or that do not inspect cloud traffic. In March 2023, 58% of all HTTP/HTTPS malware downloads originated from popular cloud apps, decreasing for the first time after four straight months of increases.
The increasing trend in cloud malware downloads has been driven partially by an increase in the number of distinct cloud apps from which malware are being downloaded. In March 2023, Netskope detected malware downloads from 162 distinct cloud apps, increasing for the third consecutive month.
Attackers achieve the most success reaching enterprise users when they abuse cloud apps that are already popular in the enterprise. Microsoft OneDrive, the most popular enterprise cloud app, has held the top spot for the most cloud malware downloads for more than six months. The other top apps for malware downloads include collaboration apps (Sharepoint), free software hosting sites (GitHub), free web hosting services (Weebly, Squarespace), and cloud storage apps (Box, Azure Blob Storage, Amazon S3, Google Drive). Webmail apps cracked the top ten again after a one-month absence, with Outlook.com coming in at number eight. Microsoft OneDrive reached a new six-month high, while Sharepoint came back down off its six-month high from February. The top ten list is a reflection of attacker tactics, user behavior, and company policy.
Top Malware File Types
By file type, Microsoft Windows Portable Executable files (EXE/DLL) accounted for the plurality of malware downloads in March, as they have for at least the past six months. Delivering malware in archive files, particularly ZIP files, had been gradually increasing but decreased for the first time since October. ZIP archives are joined in the top list by RAR, GZip, and 7 Zip files. PDF files rebounded from their six-month low in February. Malicious Plain Text files, particularly malicious PowerShell scripts and LNK files, increased for the third straight month, hitting a six month high in March. The popularity of other file types remains largely unchanged, as attackers continue to use a wide variety of file types to target their victims. Mac DMG files appeared in the top list for the first time in six months as attacker activity targeting Mac OSX users increased.
Top Malware Families
Attackers are constantly creating new malware families and new variants of existing families, either as an attempt to bypass security solutions or to update their malware’s capabilities. In March 2023, 63% of all malware downloads detected by Netskope were either new families or new variants that had not been observed in the preceding six months. The other 37% were samples that had been previously observed during the preceding six months and are still circulating in the wild.
By volume, Netskope blocks more Trojans than any other malware type. Trojans are commonly used by attackers to gain an initial foothold