Name two software tools used for OS guessing? (Choose two.

Nmap includes a built-in OS detection engine (invoked with the -O flag) that sends specially crafted probes and analyzes responses - such as TTL values, TCP window sizes, and IP ID sequences - against a database of known OS fingerprints.

Snadboy Revelation is a password recovery utility that reveals masked passwords stored in Windows dialog boxes, not an OS fingerprinting tool.

Queso is a classic dedicated OS fingerprinting tool that sends various TCP packets with specific flag combinations and matches the target's responses against a signature database to identify the remote OS.

UserInfo is a user enumeration utility used to gather account information, not a tool for identifying operating systems.

NetBus is a remote access trojan (RAT) used for unauthorized remote control of systems, not an OS fingerprinting or scanning utility.