Which of the following tools can be used by a user to hide his identity? Each correct answer represents a complete solution. Choose all that apply.

IPchains is a Linux kernel packet-filtering framework that supports IP masquerading (NAT), which rewrites the source IP address of outbound packets to hide the originating host. By routing traffic through the masquerading firewall, the real client IP is never exposed to the destination.

A rootkit is malware that conceals its presence and maintains persistent unauthorized access on a compromised system, not a tool for anonymizing network traffic or hiding user identity.

A proxy server acts as an intermediary that forwards requests to the internet on behalf of the client, presenting only the proxy's IP address to the destination server. This effectively hides the user's real IP address and can also strip identifying headers depending on the proxy configuration.

A war dialer scans telephone number ranges to discover modems and remote-access systems, and has no function related to hiding a user's network identity or IP address.

An anonymizer is a dedicated tool or service purpose-built to hide a user's identity online, typically by routing traffic through one or more intermediary servers and stripping personally identifiable metadata from requests. Unlike a general proxy, anonymizers are specifically designed with privacy protection as their primary goal.