暗箱操作

ànxiāngcāozuò
  1. covert activities (election rigging etc)
  2. under-the-table manipulations
  3. black operations

CEDICT

  1. (figurative) manipulation behind the scenes
  2. manipulation behind the scenes

Wiktionary

指利用职权暗地里做某事（多指不公正、不合法的）。

維基詞典

Entry Composition

1 暗箱 ànxiāng
  1. camera bellows
  2. camera obscura
2 操作 cāozuò
  1. to work
  2. to operate
  3. to manipulate