Advanced Web Shell Detection and Prevention: A Deep Dive into CrowdStrike's Linux Sensor Capabilities

Web shells are a significant threat to Linux servers and containers, often evading detection for long periods and enabling adversaries to maintain persistent access, execute processes, access filesystems, and tunnel network connections. These malicious scripts, frequently used in targeting critical web applications, pose high risks of data exfiltration, lateral movement, and ransomware attacks. CrowdStrike has enhanced its Falcon sensor for Linux to better detect PHP web shells, particularly those that are obfuscated or pre-existing, with features like "On write script file visibility" and "Enhance PHP visibility." These improvements have led to the detection of numerous web shells by providing real-time awareness of script activities, allowing security teams to gain a comprehensive view of adversary actions during incidents. The Falcon platform's ability to monitor script execution and dynamically evaluate PHP code increases detection efficacy and aids in analyzing sophisticated intrusions, such as those involving Zimbra mail servers. These advancements underscore the importance of enabling these detection features to safeguard against web shell threats effectively.