Which class of attacks primarily exploits public-facing services?

The class of attacks that primarily exploits public-facing services is external threats. Public-facing services, such as websites, email servers, and other internet-accessible applications, are exposed directly to potential attackers on the internet. External threats typically include tactics like hacking attempts, exploitation of software vulnerabilities, denial-of-service (DoS) attacks, and other types of cyber threats that target these services to gain unauthorized access or disrupt operations.

Insider threats refer to risks posed by individuals within the organization, such as employees or contractors, who may intentionally or unintentionally cause harm to the organization's data or systems. While these threats can be severe, they do not primarily focus on public-facing services.

Social engineering involves manipulating individuals into divulging confidential information, and while it can complement attacks on public-facing services, it does not inherently target those services directly.

Physical breaches involve unauthorized access to a physical location, such as a data center or office, to steal or damage equipment or data. While they can have cybersecurity implications, they do not specifically exploit public-facing services in the same way that external threats do.

Thus, focusing on external threats makes it clear they are designed to compromise or disrupt public-facing services directly.