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The Secure Shell Protocol (SSH) is a cryptographic network protocol for operating network services securely over an unsecured network. Its most notable applications are remote login and command-line execution.
Telnet is a client/server application protocol that provides access to virtual terminals of remote systems on local area networks or the Internet. It is a protocol for bidirectional 8-bit communications. Its main goal was to connect terminal devices and terminal-oriented processes.
The File Transfer Protocol (FTP) is a standard communication protocol used for the transfer of computer files from a server to a client on a computer network. FTP is built on a client–server model architecture using separate control and data connections between the client and the server. FTP users may authenticate themselves with a plain-text sign-in protocol, normally in the form of a username and password, but can connect anonymously if the server is configured to allow it. For secure transmission that protects the username and password, and encrypts the content, FTP is often secured with SSL/TLS (FTPS) or replaced with SSH File Transfer Protocol (SFTP).
In computer networking, a proxy server is a server application that acts as an intermediary between a client requesting a resource and the server providing that resource. It improves privacy, security, and possibly performance in the process.
In computer security, a DMZ or demilitarized zone is a physical or logical subnetwork that contains and exposes an organization's external-facing services to an untrusted, usually larger, network such as the Internet. The purpose of a DMZ is to add an additional layer of security to an organization's local area network (LAN): an external network node can access only what is exposed in the DMZ, while the rest of the organization's network is protected behind a firewall. The DMZ functions as a small, isolated network positioned between the Internet and the private network.
Squid is a caching and forwarding HTTP web proxy. It has a wide variety of uses, including speeding up a web server by caching repeated requests, caching World Wide Web (WWW), Domain Name System (DNS), and other network lookups for a group of people sharing network resources, and aiding security by filtering traffic. Although used for mainly HTTP and File Transfer Protocol (FTP), Squid includes limited support for several other protocols including Internet Gopher, Secure Sockets Layer (SSL), Transport Layer Security (TLS), and Hypertext Transfer Protocol Secure (HTTPS). Squid does not support the SOCKS protocol, unlike Privoxy, with which Squid can be used in order to provide SOCKS support.
SOCKS is an Internet protocol that exchanges network packets between a client and server through a proxy server. SOCKS5 optionally provides authentication so only authorized users may access a server. Practically, a SOCKS server proxies TCP connections to an arbitrary IP address, and provides a means for UDP packets to be forwarded. A SOCKS server accepts incoming client connection on TCP port 1080, as defined in RFC 1928.
In computer networking, port forwarding or port mapping is an application of network address translation (NAT) that redirects a communication request from one address and port number combination to another while the packets are traversing a network gateway, such as a router or firewall. This technique is most commonly used to make services on a host residing on a protected or masqueraded (internal) network available to hosts on the opposite side of the gateway, by remapping the destination IP address and port number of the communication to an internal host.
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). A variant called single packet authorization (SPA) exists, where only a single "knock" is needed, consisting of an encrypted packet.
In computer networks, a tunneling protocol is a communication protocol which allows for the movement of data from one network to another. It can, for example, allow private network communications to be sent across a public network, or for one network protocol to be carried over an incompatible network, through a process called encapsulation.
inetd is a super-server daemon on many Unix systems that provides Internet services. For each configured service, it listens for requests from connecting clients. Requests are served by spawning a process which runs the appropriate executable, but simple services such as echo are served by inetd itself. External executables, which are run on request, can be single- or multi-threaded. First appearing in 4.3BSD, it is generally located at /usr/sbin/inetd. inetd is based on the (service) activator pattern
Network address translation traversal is a computer networking technique of establishing and maintaining Internet Protocol connections across gateways that implement network address translation (NAT).
A proxy auto-config (PAC) file defines how web browsers and other user agents can automatically choose the appropriate proxy server for fetching a given URL.
An application-level gateway is a security component that augments a firewall or NAT employed in a mobile network. It allows customized NAT traversal filters to be plugged into the gateway to support address and port translation for certain application layer "control/data" protocols such as FTP, BitTorrent, SIP, RTSP, file transfer in IM applications. In order for these protocols to work through NAT or a firewall, either the application has to know about an address/port number combination that allows incoming packets, or the NAT has to monitor the control traffic and open up port mappings dynamically as required. Legitimate application data can thus be passed through the security checks of the firewall or NAT that would have otherwise restricted the traffic for not meeting its limited filter criteria.
A proxy list is a list of open HTTP/HTTPS/SOCKS proxy servers all on one website. Proxies allow users to make indirect network connections to other computer network services. Proxy lists include the IP addresses of computers hosting open proxy servers, meaning that these proxy servers are available to anyone on the internet. Proxy lists are often organized by the various proxy protocols the servers use. Many proxy lists index Web proxies, which can be used without changing browser settings.
HTTP 403 is an HTTP status code meaning access to the requested resource is forbidden. The server understood the request, but will not fulfill it, if it was correct.
In computing, Microsoft's Windows Vista and Windows Server 2008 introduced in 2007/2008 a new networking stack named Next Generation TCP/IP stack, to improve on the previous stack in several ways. The stack includes native implementation of IPv6, as well as a complete overhaul of IPv4. The new TCP/IP stack uses a new method to store configuration settings that enables more dynamic control and does not require a computer restart after a change in settings. The new stack, implemented as a dual-stack model, depends on a strong host-model and features an infrastructure to enable more modular components that one can dynamically insert and remove.
A distributed firewall is a security application on a host machine of a network that protects the servers and user machines of its enterprise's networks against unwanted intrusion. A firewall is a system or group of systems that implements a set of security rules to enforce access control between two networks to protect the "inside" network from the "outside" network. They filter all traffic regardless of its origin—the Internet or the internal network. Usually deployed behind the traditional firewall, they provide a second layer of defense. The advantages of the distributed firewall allow security rules (policies) to be defined and pushed out on an enterprise-wide basis, which is necessary for larger enterprises.
OpenSSH is a suite of secure networking utilities based on the Secure Shell (SSH) protocol, which provides a secure channel over an unsecured network in a client–server architecture.
The Ident Protocol, specified in RFC 1413, is an Internet protocol that helps identify the user of a particular TCP connection. One popular daemon program for providing the ident service is identd.