Main problem with security is trust. How can one trust the security app which is offered as a service and believe that it will not do anything malicious? It is

Main problem with security is trust. How can one trust the security app which is offered as a service and believe that it will not do anything malicious? It is like storing my bank password and all credit card details in another thirdparty site. As a user I do not trust any thirdparty service which offers to store passwords. Similarly as a developer I do not trust any third party service over web for websecurity testing.