Malicious Lua Script with Shell Command

This rule detects the presence of the string "io.popen(" within HTTP response data. This string is indicative of a Lua script attempting to execute shell commands, which is a common technique used by malware to achieve arbitrary code execution on a compromised system. The rule specifically looks for this pattern in data flowing from the server to the client (flow:to_client), suggesting a malicious script being delivered to a user's browser or an application.