The central idea behind layered security or defense is that in order to protect systems from a broad range of attacks, using multiple strategies will be more effective. Layered security can involve security protocols at the system or network levels, at the application level, or at the transmission level, where security experts may focus on data in use over data at rest.

Layered security efforts attempt to address problems with different kinds of hacking or phishing, denial of service attacks and other cyberattacks, as well as worms, viruses, malware and other kinds of more passive or indirect system invasions.