In hping3, which type of scan is performed with the -A option?

• A. ACK scan
• B. SYN scan
• C. UDP scan
• D. FIN scan

Answer: (A)

Using the ACK flag in hping3 creates an unsolicited TCP acknowledgment packet, which is used for an ACK scan. This type of scan isn’t about opening a connection; it tests how the target’s firewall or filtering treats stray ACKs. If a port is unfiltered, the target typically responds with a TCP RST; if the port is filtered, there may be no reply or an ICMP error. So -A corresponds to an ACK scan, aimed at mapping filtering behavior rather than whether a port is open or closed. Other scan types rely on different flags (SYN for a half-open SYN scan, FIN with FIN scans, UDP for UDP scans), which is why they aren’t produced by the -A option.