Keystroke logging is used by attackers to record everything a person types, including usernames, passwords, and account information. Keystroke logging is a method of logging and recording user keystrokes. It can be performed with software or hardware devices. Keystroke logging devices can record everything a person types using his keyboard, such as to measure employee's productivity on certain clerical tasks. These types of devices can also be used to get usernames, passwords, etc. Answer: D is incorrect. Wiretapping is used to eavesdrop on voice calls. Eavesdropping is the process of listening in on private conversations. It also includes attackers listening in on network traffic. Answer: C 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: A is incorrect. Packet sniffing is a process of monitoring data packets that travel across a network. The software used for packet sniffing is known as sniffers. There are many packet-sniffing programs that are available on the Internet. Some of these are unauthorized, which can be harmful for a network's security.