ICQ / IRC
ICQ (from English I seek you - “I am looking for you”) is a centralized instant messaging service on the Internet, currently owned by the Mail.ru Group investment fund. ICQ is a centralized instant messaging service using the OSCAR protocol. The service user works with a client program running on a device connected to the Internet. The messenger connects to the server. Through the server, search and communication with other clients is carried out, and the exchange of service data, messages between users can be carried out either through the server or without its participation. As in most powerful network systems that serve a huge number of client requests, this server is not the only one and some of them are server clusters.
The service is commercial, but its use is free. Since its inception, the service has belonged to its developer, Mirabilis, in 1998 it was sold to the American company AOL, and in April 2010 to the Russian investment fund Digital Sky Technologies (DST). After the reorganization of DST in September 2010, ICQ became part of the Mail.Ru Group.
Over the years, ICQ has released many clients and has undergone many changes. As of September 2013, the total monthly ICQ audience in Russia is 7.9 million (in the world - 12.3 million), at the end of 2014: in Russia - 6.7 million, in the world - 11 million.
IRC (Internet Relay Chat) is an application-level protocol for real-time messaging. Designed primarily for group communication, it also allows you to communicate through private messages and share data, including files.
IRC uses the TCP transport protocol and cryptographic TLS (optional).
The IRC began to gain particular popularity after Operation Desert Storm (1991), when messages from all over the world gathered in one place and were broadcast on-line in IRC.
Due to the technical simplicity of implementation, the IRC protocol has recently been used in organizing botnets as a means of transmitting control commands to computers participating in the botnet from the owner.