Which of the following techniques are NOT used to perform active OS fingerprinting? Each correct answer represents a complete solution. Choose all that apply.

Analyzing email headers is a passive reconnaissance technique that extracts OS or mail-server information from existing message metadata without sending any probe to the target system.

Sniffing and analyzing packets is also a passive technique - it captures traffic already on the network rather than actively injecting probes to elicit OS-specific responses.

ICMP error message quoting IS an active fingerprinting technique because it sends packets designed to trigger ICMP errors and then analyzes how the target OS quotes back the original message, which varies by implementation.

Sending FIN packets to open ports IS an active fingerprinting technique that exploits OS-specific differences in TCP/IP stack behavior, such as whether the target responds with RST or silently drops the packet.