Isabel is responsible for security at a mid-sized company. She wants to prevent users on her network from visiting job-hunting sites while at work. Which of the following would be the best device to accomplish this goal?

A web proxy can be used to block certain websites. It is common practice for network administrators to block either individual sites or general classes of sites (like job-hunting sites).
Network address translation (NAT) is used to translate the private IP addresses of internal computers to public IP addresses.
A packet filter firewall can block traffic on a given port or IP address or using a particular protocol, but generally, they are unable to block specific websites.
Network-based intrusion prevention systems (NIPSs) identify and block attacks; they cannot prevent users from visiting specific websites.