← Let replies in, keep new connections out

Solve in your browser

Edit the files below. The Objectives tick green live as you work. Hit Check when they all pass and your verified proof page is issued automatically.

Objectives

  • Met: Return traffic for connections the inside started is allowed back in
  • Not met: A new, unsolicited connection from the outside is denied
  • Met: Inside hosts can still initiate outbound connections

2 of 3 objectives met.

Objectives update live as you edit. Hitting Check commits your proof.

No account needed to explore. When you're ready, browse the rest of the challenges or sign in to save a solve as a verified proof.