Methods and systems for penetration testing of a networked system by a penetration testing system. In some embodiments, both active and passive validation methods are used during a single penetration testing campaign in a single networked system. In other embodiments, a first penetration testing campaign uses only active validation and a second penetration campaign uses only passive validation, where both campaigns are performed by a single penetration testing system in a single networked system. Node-by-node determination of whether to use active or passive validation can be based on expected extent and/or likelihood of damage from actually compromising a network node using active validation.