Which surveillance technology captures how data is entered into a system?

The surveillance technology that captures how data is entered into a system is a keylogger. Keyloggers are designed to monitor and record keystrokes on a keyboard, allowing them to capture everything a user types, including passwords, messages, and other sensitive information. This capability makes keyloggers particularly effective for malicious purposes, such as stealing personal data or login credentials.

In contrast, firewalls primarily serve as a security measure to control incoming and outgoing network traffic based on predetermined security rules, rather than monitoring keystrokes. Intrusion Detection Systems (IDS) are designed to detect and respond to unauthorized access attempts or activities within a network but do not focus on the data that is entered into a system. Data Loss Prevention (DLP) solutions aim to prevent sensitive data from being accessed, shared, or leaked outside an organization, without capturing specific keystrokes or direct user input. Thus, keyloggers are uniquely positioned to fulfill the role described in the question by directly tracking user input.