Kautilya's Arthashastra 13.3.58

13.3.58

grāmaghātapraviṣṭāṃ vā vikṣipya bahudhāṭavīm /
ghātayed iti corāṇām apasarpāḥ prakīrtitāḥ //E

Those spies, who enter into the wild tracts of the enemy with the intention of plundering his villages, and who, leaving that work, set themselves to destroy the enemy, are termed spies under the garb of thieves.