Explanation: Brute force attack is the most likely cause of the account lockouts. In a brute force attack, unauthorized users attempt to log on to a network or a computer by using multiple possible user names and passwords. Windows 2000 and other network operating systems have a security feature that locks a user account if the number of failed logon attempts occur within a specified period of time, based on the security policy lockout settings. Answer: A is incorrect. Spoofing is a technique that makes a transmission appear to have come from an authentic source by forging the IP address, email address, caller ID, etc. In IP spoofing, a hacker modifies packet headers by using someone else’s IP address to hide his identity. However, spoofing cannot be used while surfing the Internet, chatting on-line, etc. because forging the source IP address causes the responses to be misdirected. Answer: C is incorrect. A SYN attack affects computers running on the TCP/IP protocol. It is a protocol-level attack that can render a computer’s network services unavailable. A SYN attack is also known as SYN flooding. Answer: D is incorrect. When a computer repeatedly sends ICMP echo requests to another computer, it is known as a PING attack.