Microsoft published an interesting report that investigates web shell attacks, the IT giant says it detects 77,000 active web shells daily.

According to a report published by Microsoft, the company detects an average of 77,000 active web shells, spreading across 46,000 infected servers, on a daily base.

A web shell is a code, often written in typical web development programming languages (e.g., ASP, PHP, JSP), that attackers implant on web servers to gain remote access and code execution.

Microsoft observed several threat groups, including ZINC, KRYPTON, and GALLIUM, using these malicious codes in their campaigns. Threat actors use to exploit known issues in web applications to compromise web server and install the web shells. One of the most widely adopted web shells is the China Chopper one that was employed in numerous cyberespionage campaigns carried out by China-linked APT groups.

In October 2018, security agencies belonging to Five Eyes (United States, United Kingdom, Canada, Australia and N ew Zealand) have released a joint report that details some p opular hacking tools, including China Chopper.

77,000 detections on a daily base are worrisome figure and could give us an indication of the intense activity of threat actors in cyberspace.

“Unfortunately, these gaps appear to be widespread, given that every month, Microsoft Defender Advanced Threat Protection (ATP) detects an average of 77,000 web shell and related artifacts on an average of 46,000 distinct machines.” reads the report published by Microsoft.

“Because web shells are a multi-faceted threat, enterprises should build comprehensive defenses for multiple attack surfaces.” concludes Microsoft. ” Gaining visibility into internet-facing servers is key to detecting and addressing the threat of web shells. The installation of web shells can be detected by monitoring web application directories for web script file writes. Applications such as Outlook Web Access (OWA) rarely change after they have been installed and script writes to these application directories should be treated as suspicious. “

Pierluigi Paganini