Organized criminals and malicious hackers use the Internet to exploit personal computer security vulnerabilities, allowing them to capture your personal data. Trojans (short for Trojan Horse) are programs designed to give a criminal access to your PC. With access, the criminal can install additional software on your PC. One popular type of program is a key logger. A key logger records every key you type (including account numbers, and passwords); collects them; and sends them to a server from which the criminal can retrieve the data.