The Spam filter was released on 27 May 2009, with the Dungeon maps and spam filter update. The filter is accessed through the "Game" tab in the chat interface. It filters out repetitive messages like "You catch a tuna.". Jagex claims that over 2,900 types of messages will now be filtered. However, important messages (i.e. such as a warning stating that the player is being burnt by dragonfire) will still appear even if the spam filter is active.
Prior to this update, when a player trained in a particular skill, the "Game" messages window would often fill up with these repeated unnecessary messages.
Dungeoneering "Spam" messages, have now been fixed due to a small update on 15 March 2011.