OysterLoader C2 HTTP User-Agent and Endpoints

Daniel Jeremiah@daniyyell

•updated Feb 20, 2026•0•17

This rule detects OysterLoader C2 communication based on specific HTTP User-Agent strings and URI paths. It looks for 'WordPressAgent' or 'FingerPrint' in the User-Agent field combined with URIs like '/reg', '/login', '/api/kcehc', '/api/v2/init', '/api/v2/facade', or '/api/jgfnsfnuefcnegfnehjbfncejfh'. This activity is indicative of OysterLoader's multi-stage evasion techniques as described in a Sekoia report.