The rule "BPF filter applied using TC" is designed to detect suspicious activity involving the use of the `tc` command in Linux, specifically when it sets a BPF (Berkeley Packet Filter) on a network interface. The command `tc` allows configuration of traffic control in the Linux kernel and can ultimately manipulate incoming traffic. Although usage of `tc` for setting BPF filters is rare in legitimate scenarios, a threat actor may exploit this command to illicitly manage or surveil network traffic. This rule triggers when it detects the execution of the `/usr/sbin/tc` binary with specific arguments that indicate BPF filtering, while excluding benign contexts involving virtualization processes like `libvirtd`. The alert aims to flag potentially malicious activity, warranting further investigation into the command's execution, the associated user context, and overall system behavior. Should the alert trigger, security teams are advised to review surrounding network logs, confirm the legitimacy of the process, and take appropriate remediation steps such as isolating affected systems to mitigate risks.