What is 死間 in English and is there a second way in English that could describe this?
The term 死間 (doomed spies) came from the last chapter of 《孫子兵法》(The Art of War)

13: 用間 - The Use of Spies


  http://ctext.org/art-of-war/use-of-spies
  
  用間:
  故用間有五：有鄉間、有內間、有反間、有死間、有生間。五間俱起，莫知其道，是謂神紀，人君之寶也。鄉間者，因其鄉人而用之。內間者，因其官人而用之。反間者，因其敵間而用之。死間者，為誑事于外，令吾間知之，而傳于敵。生間者，反報也。
  
  Hence the use of spies, of whom there are five classes: (1) Local spies; (2) inward spies; (3) converted spies; (4) doomed spies; (5) surviving spies. When these five kinds of spy are all at work, none can discover the secret system.
  
  Having doomed spies, doing certain things openly for purposes of deception, and allowing our spies to know of them and report them to the enemy. 


In modern term, 死間 (doomed spies) are basically "deception / sabotage agents" Their actions are visible. In contrast to 生間 (surviving spies) , whose main function are to secretly gather and report information to their own state.