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In computer networking, port knocking is a method of externally opening ports on a firewall by generating a connection attempt on a set of prespecified closed ports. Once a correct sequence of connection attempts is received, the firewall rules are dynamically modified to allow the host which sent the connection attempts to connect over specific port(s).
This is a list of TCP and UDP port numbers used by protocols for operation of network applications. The Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP) only need one port for bidirectional traffic. TCP usually uses port numbers that match the services of the corresponding UDP implementations, if they exist, and vice versa.
The new connection attempt punches a hole in the client's firewall as the endpoint now becomes open to receive a response from its peer. Depending on network conditions, one or both clients might receive a connection request. Successful exchange of an authentication nonce between both clients indicates the completion of a hole punching ...
In computer networking, a firewall pinhole is a port that is not protected by a firewall to allow a particular application to gain access to a service on a host in the network protected by the firewall. [1] [2] Leaving ports open in firewall configurations exposes the protected system to potentially malicious abuse.
In computer networking, a port or port number is a number assigned to uniquely identify a connection endpoint and to direct data to a specific service. At the software level, within an operating system , a port is a logical construct that identifies a specific process or a type of network service .
Against some port knocking designs, DoS attacks are a major problem, but against othes, they are impratical or would require massive resources to be effective. Again, see this for descriptions of port knocking designs. DoS attacks are a weakness of certain specific designs, not a systemic flaw in the port knocking concept.
UDP hole punching is a method for establishing bidirectional UDP connections between Internet hosts in private networks using network address translators. The technique is not applicable in all scenarios or with all types of NATs, as NAT operating characteristics are not standardized.
In computer networking, TCP Stealth is a proposed modification of the Transmission Control Protocol (TCP) to hide open ports of some TCP services from the public, in order to impede port scans. It is somewhat similar to the port knocking technique. [1] [2] As of May 2015 it is an IETF Internet Draft specification. [3]