明枪好躲，暗箭难防
míng​qiāng​hǎo​duǒ'àn​jiàn​nán​fáng

it is hard to guard against secret conspiracies

明枪好躲，暗箭难防 明槍好躲，暗箭難防 míng​qiāng​hǎo​duǒ'àn​jiàn​nán​fáng
it is hard to guard against secret conspiracies
(idiom) easy to dodge a spear in the open but hard to avoid an arrow in the dark; it is easier to defend against an open attack than a hidden plot