明枪易躲，暗箭难防
míng​qiāng​yì​duǒ'àn​jiàn​nán​fáng

it is hard to guard against secret conspiracies

明枪易躲，暗箭难防 明槍易躲，暗箭難防 míng​qiāng​yì​duǒ'àn​jiàn​nán​fáng
it is hard to guard against secret conspiracies
literally meaning it is easy to dodge a spear in the open, but hard to avoid an arrow in the dark; used to say that overt attacks are easier to handle than secret plots or betrayal from behind one's own side