Cyberspace, or the Internet, supports important commercial assets as well as non-commercial assets. A hacker, a state or nonstate agent, or a cybercriminal can attack cyberspace for financial, political, or espionage reasons, or to steal identities, or to cause the disruption of critical infrastructure. We have achieved great advancement in computing systems in both hardware and software and their security. On the other hand, we still see massive cyberattacks that result in enormous data losses. Recent attacks have included sophisticated cyberattacks targeting many institutions, including those who provide management and host the core parts of Internet infrastructure. The number and types of attacks, the duration of attacks, and their complexity are all on the rise.