# Ports Open/Close

{% hint style="info" %}
With **BOLD** is the attacker/client send flags
{% endhint %}

### TCP Connect 

open: **SYN**, SYN/ACK, ACK, **RST** 

close: **SYN**, RST

### Stealth Scan(Half Open) 

open: **SYN**, SYN/ACK, **RST** 

close: **SYN**, RST

### Inverse TCP flag 

open: **FIN/URG/PSH/NULL**, No Response 

close: **FIN/URG/PSH/NULL**, RST/ACK

### Xmas Scan 

open: **FIN+URG+PSH**, No Response 

close: **FIN+URG+PSH**, RST/ACK

### Null Scan 

open: No Response 

close: RST

### ACK flag Probe Scanning 

Attacker/client sends only ACK package. If he receives on **RST** flag that means the port is there and **open**. Also on "NO RESPONSE" means that a stateful firewall is present. On a RST flag means no firewall is in place.

### IDLE Scan(sends packets from IDLE zombie)

### UDP Scanning(No flags sent, No 3-way Handshake made) 

open: No Response 

close: ICMP port unreadable UDP port scanning is often unreliable, as firewalls and routers may drop ICMP packets. This can lead to false positives in your scan, and you will regularly see UDP port scans showing all UDP ports open on a scanned machine. People often forget to scan for UDP services, and stick only to TCP scanning, thereby seeing only half of the equation.

###

### FIN Scanning 

open: No Response 

close: RST

###

### ACK Scanning 

open: RST 

close: No Response


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