I personally know "Gnostic" groups that have been infiltrated by the black lodge after performing investigations and being warned by my Inner God. So it is possible, and I must say it is heart-wrenching to know about such cases. However, do not be so quick to jump to conclusions or to publicly accuse others if you suspect conscious acts of sorcery in spiritual groups, because that can incur serious karma. This is why in many cases I have had to remain silent, yet in relation with sincere seekers who are reading the "warning signs" of certain institutions, it has been necessary to speak.
To really know the purity of any organization, one must awaken, study the great scriptures, and follow the heart. It is in this way, through a strong intellectual-spiritual culture and cognizance of its principles within our daily life, that we will be defended against the afflictive snares of the tenebrous ones. While we must reserve our judgment, we must also listen to the voice of the silence within our heart, acknowledging that secret inclination within our being if we feel something is wrong. It is sad to see that many so-called "spiritual" seekers throw away their common sense when entering esotericism. It is truly lamentable, since in many cases, our common sense and sincere reflection will prevent many occurrences of deception, most especially in relation with our own minds!
Joyful in hope, suffering in tribulation, be thou constant in thy prayer.
Benedictis, qui venit in nomine Domini. Osanna in excelsis.
"Blessed is he who comes in the name of the Lord. Hosanna in the highest!"