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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 51% of all malware downloads in July originating from 155 cloud apps.
- Microsoft Live Outlook users were targeted with a widespread phishing campaign containing a PDF attachment that urged victims to update their Amazon billing details.
- The RagnarLocker and Rhysidia ransomware were among the top malware families detected on the Netskope platform in August.
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 August 2023, 51% of all HTTP/HTTPS malware downloads originated from popular cloud apps, decreasing from July but still above its six month low of 49%.
The total number of cloud apps from which malware downloads originated also fell slightly, with malware downloads originating from 155 distinct cloud apps.
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. For four straight months, the percentage of cloud malware downloads originating from Microsoft OneDrive had fallen, but appears to have stabilized at 23% in August. Malware downloads from Microsoft Live Outlook increased significantly in August, propelling it into the second place spot for the first time. Otherwise, the top ten apps remained largely unchanged and included free software hosting sites (GitHub), collaboration apps (SharePoint), free web hosting services (Weebly), cloud storage apps (Azure Blob Storage, Google Drive, Amazon S3), webmail apps (Outlook.com), and document sharing apps (DocPlayer). In total, the top ten accounted for two-thirds of all cloud malware downloads, with the remaining one-third spread over 145 other cloud apps. The top ten list is a reflection of attacker tactics, user behavior, and company policy.