CREST is widely known in the penetration testing indusry, due to CREST’s professional membership scheme, professional certification for penetraiton testers, and support towards becoming CHECK with NCSC.
Ann excert from CREST’s website regarding membership:
In accordance with CREST’s stated aim “to increase professionalism in the security testing industry”, CREST places requirements on member companies in order to ensure that consistent standards of services are delivered.
It is worth noting that as covered in the FAQ provided by CREST, obtaining organisational membership is not dependant on people holding CREST-based certifications.
For full guidance on joining CREST as an organisational member (for organisations), the following link will be of help: click here