Please see ICC's Fair Play & Community Policy here:
https://www.chessclub.com/fairplay
While cheating does occur, ICC takes cheating very seriously and monitors games 24x7. If you suspect a player has cheated, please file a complaint. Please describe why you feel the player is cheating and provide any supporting evidence. Also, note that the ICC Fair-Play system detects cheating, so if you’ve only played a single game against the player in question, you may want to wait for more games against the same player before filing a report.