Final answer:
A buffer overflow in Microsoft Windows 2000/XP LSASS was exploited by attackers.
Step-by-step explanation:
A buffer overflow is a type of software vulnerability that occurs when a program tries to write more data into a buffer than it can hold. In the case of the Microsoft Windows 2000/XP Local Security Authority Subsystem Service (LSASS), a buffer overflow vulnerability was exploited by attackers. This allowed them to gain unauthorized access to the system and execute malicious code.