Rybka is a computer chess engine designed by International Master Vasik Rajlich. Around 2011, Rybka was one of the top-rated engines on chess engine rating lists and won many computer chess tournaments. After Rybka won four consecutive World Computer Chess Championships from 2007 to 2010, it was stripped of these titles after the International Computer Games Association concluded in June 2011 that Rybka was plagiarized from both the Crafty and the Fruit chess engines and so failed to meet their originality requirements. In 2015, FIDE Ethics Commission, following a complaint put forward by Vasik Rajlich and chess engine developer and games publisher Chris Whittington regarding ethical breaches during internal disciplinary proceedings, ruled the ICGA guilty and sanctioned ICGA with a warning. Case 2/2012. ChessBase published a challenging two-part interview-article about the process and verdict with ICGA spokesperson David Levy. Subsequently, ChessBase has published Rybka to produce Fritz 15 released in late 2015 and Fritz 16 released in late 2017. Name The word rybka, pronounced in Czech, means little fish in Czech, Polish, and in many other Slavic languages. Vasik Rajlich was once asked in an interview by Alexander Schmidt, "Did you choose the name Rybka because your program always slipped out of your hands like a little fish?" He replied, "As for the name Rybka – I am sorry but this will remain my private secret." Internals Rybka is a closed-source program, but still some details have been revealed: Rybka uses a bitboard representation, and is an alpha-beta searcher with a relatively large aspiration window. It uses very aggressive pruning, leading to imbalanced search trees. The details of the evaluation function are unknown, but since version 2.3.1 it has included work by GM Larry Kaufman on material imbalances, much of which was worked out in a series of papers in the 1990s. Team Several members of the Rybka team are strong chess players: Vasik Rajlich, the main author of Rybka is an International Master (IM). GM Larry Kaufman is the 2008 Senior Chess World Champion, and from version 2.3 through version 3 was in primary charge of the evaluation function. Iweta Rajlich, Vasik Rajlich's wife and the main Rybka tester is a Women's GM (WGM) and IM. Jeroen Noomen (who used to work on Rebel) and Dagh Nielsen were the authors of its opening book – the latter is one of the world's top freestyle chess players. Both are now