A mitigation service can monitor network traffic in one direction between a client computer and a server computer. The mitigation service can receive a request from a client computer to establish a network connection with a server computer. The mitigation service can reply to the client computer with an acknowledgment that is configured to cause the client computer to issue a request to reset the connection. The acknowledgement is configured not to affect the establishment of the network connection with the server computer. The mitigation service can compare the details of the reset request with the request to establish the network connection. If the details match, the mitigation service can forward the request to establish the network connection to the server computer.