暗箭难防

Explanation: Lengjian the most difficult to prevent. Analogy machinations difficult to prevent. 　　Usage: The main predicate; as predicate, object; metaphor means is difficult to prepare for conspiracy 　　Source: "Ancient and Modern Drama Liu thousands of horned cattle to fight disease," the second fold: "babe also, one to say: better to hide the gun, stab in the back hard against. I plot against him, moved to come, then punch down with that fellow, save you father. " 　　Examples: Haier is also a good gun to hide the note, ~. (Yuan Anonymous "cow horn") Thesaurus:  False friends are worse than bitter enemies., Good hide out gun