Pulse Secure April Attack
Pulse Connect Secure vulnerability CVE-2021-22893 and other old vulnerabilities are being actively exploited. While GRIMM engineers were not able to obtain a device or the firmware for a full analysis, the device in question looks like a Linux-based rack-mounted server that sits inside the firewall and mediates all kinds of access for clients accessing it via a web interface. Based on the available information, it appears weaknesses in the web application within the device have been the root of multiple problems, including the most recent vulnerability. Takeaway This was not a supply chain attack, this was a sophisticated actor becoming intimately familiar with a target and exploiting it persistently, continuing to find new vulnerabilities and tailoring their malware to blend in with the software. The signs are subtle but detectable: changes in hashes on the device, strange authentication behavior appearing in logs, small changes in network traffic such as new HTTP verbs and extr