About the Cisco Secure Client System Extension
Cisco Secure Client uses a network system extension on macOS 11 (and later), bundled into an application named Cisco Secure Client - Socket Filter. The app controls the extension activation and deactivation and is installed under /Applications/Cisco.
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DNS proxy
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App/transparent proxy
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Content filter
Cisco Secure Client requires its system extension and all its components to be active for proper operation, which implies that the mentioned components are all present and show as green (running) in the left pane of the macOS Network UI.