After reading the sample letter I identified the first theory which was a veiled Denial of responsibility from the neutralization theory. The letter was written in a way that the owners of the website showed that the responsible party was the third party that provided the website services. Another one is structural functionalism. People expect a certain degree of protection from “reputable” website. They get really upset when they receive letters of breaches especially ones that were attacked for a long period of time without being notice.
In terms of economic theory one can infer rational choice because the company used a third party vendor to not have to worry about cybersecurity. We can also infer Laissez-fare economic theory because the company point to a government website to learn more about the problem at hand. Either way the person affected is the user and the guilty parties point to one another to avoid responsibility.