One reason that marketing cyber security to potential clients is so difficult is because all companies expect that their vendors should and will be "taking care" of the problem themselves. As a result, businesses don't do a good job of managing the risks involved in sharing data with third-party vendors.
When marketing your cyber security services to clients, educate them about the risks involved in passing their data to vendors. One of the greatest challenges in cyber security marketing is educating potential customers that cyber risk is not just an IT problem, but actually a business problem.
Your marketing messages should educate prospects and help them understand that cyber security is not only a business problem, but also, more specifically, a vendor management problem.