Nmap은 다양한 스캐닝 방법을 사용하여 동일한 포트의 다양한 상태를 표시합니다.

IP 주소의 -sA 스캔을 시작하면 포트 "80"이 "필터링되지 않음"으로 표시됩니다. 코드는 아래와 같이 표시됩니다.

sudo nmap -sA -vv -p 80 192.168.0.30 -Pn
Host discovery disabled (-Pn). All addresses will be marked 'up' and scan times may be slower.
Starting Nmap 7.92 ( https://nmap.org ) at 2022-03-24 01:09 EDT
Initiating ARP Ping Scan at 01:09
Scanning 192.168.0.30 [1 port]
Completed ARP Ping Scan at 01:09, 1.34s elapsed (1 total hosts)
Initiating Parallel DNS resolution of 1 host. at 01:09
Completed Parallel DNS resolution of 1 host. at 01:09, 0.37s elapsed
Initiating ACK Scan at 01:09
Scanning 192.168.0.30  [1 port]
Completed ACK Scan at 01:09, 0.73s elapsed (1 total ports)
Nmap scan report for 192.168.0.30
Host is up, received arp-response (1.1s latency).
Scanned at 2022-03-24 01:09:50 EDT for 0s

PORT   STATE      SERVICE REASON
80/tcp unfiltered http    reset ttl 64

그러나 -sT와 같은 스캔 유형을 시작하면 포트 "80"이 "닫힘"으로 표시됩니다. 코드는 아래와 같이 표시됩니다.

sudo nmap -sT -vv -p 80 192.168.0.30 -Pn
Host discovery disabled (-Pn). All addresses will be marked 'up' and scan times may be slower.
Starting Nmap 7.92 ( https://nmap.org ) at 2022-03-24 01:15 EDT
Initiating Parallel DNS resolution of 1 host. at 01:15
Completed Parallel DNS resolution of 1 host. at 01:15, 0.24s elapsed
Initiating Connect Scan at 01:15
Scanning 192.168.0.30 [1 port]
Completed Connect Scan at 01:15, 0.25s elapsed (1 total ports)
Nmap scan report for 192.168.0.30
Host is up, received user-set (0.25s latency).
Scanned at 2022-03-24 01:15:03 EDT for 0s

PORT   STATE  SERVICE REASON
80/tcp closed http    conn-refused

왜 이런 일이 발생하는지, 정상적인 경우인지 알고 싶습니다. 또한 이 예와 같이 포트를 닫고 필터링하지 않을 수 있습니까?