Application vulnerability was the most feared threat for 73 percent of respondents to a 2011 study by (ISC)2. A robust application security program should take a multi-layered approach that addresses the operating system, the network layer and the development of the code itself. With every code update, a new risk can be created, and even interactions between applications can cause unanticipated security problems. There is no silver bullet for application security; instead, it requires a disciplined effort that involves time, money and people.”]
Source: https://www.csoonline.com/article/2131380/layered-defense-for-software-applications.html