Approaches for preventing TCP RST attacks intended to cause denial of service in packet-switched networks are disclosed. In one approach, upon receiving a TCP RST packet, an endpoint node determines whether the TCP segment contains valid authentication information. The TCP RST segment is accepted and the TCP connection is closed only when the authentication information is valid. Authentication information may comprise a reset type values, and either initial sequence numbers of both endpoints, or a copy of a TCP header and options values previously sent by the endpoint node that is performing the authentication. Thus, attacks are thwarted because an attacker cannot know or reasonably guess the required authentication information.