Which Type of scan sends a packets with no flags set? Select the Answer

A.
Open Scan

B.
Null Scan

C.
Xmas Scan

D.
Half-Open Scan

Explanation:
The types of port connections supported are:
•TCP Full Connect. This mode makes a full connection to the target’s TCP ports and can save any

data or banners returned from the target. This mode is the most accurate for determining TCP
services,but it is also easily recognized by Intrusion Detection Systems (IDS).
•UDP ICMP Port Unreachable Connect. This mode sends a short UDP packet to the target’s UDP
ports and looks for an ICMP Port Unreachable message in return. The absence of that message
indicates either the port is used,or the target does not return the ICMP message which can lead to
false positives. It can save any data or banners returned from the target. This mode is also easily
recognized by IDS.
•TCP Full/UDP ICMP Combined. This mode combines the previous two modes into one operation.
•TCP SYN Half Open. (Windows XP/2000 only) This mode sends out a SYN packet to the target
port and listens for the appropriate response. Open ports respond with a SYN|ACK and closed
ports respond with ACK|RST or RST. This mode is less likely to be noted by IDS,but since the
connection is never fully completed,it cannot gather data or banner information. However,the
attacker has full control over TTL,Source Port,MTU,Sequence number,and Window parameters in
the SYN packet.
•TCP Other. (Windows XP/2000 only) This mode sends out a TCP packet with any combination of
the SYN,FIN,ACK,RST,PSH,URG flags set to the target port and listens for the response.
Again,the attacker can have full control over TTL,Source Port,MTU,Sequence number,and
Window parameters in the custom TCP packet. The Analyze feature helps with analyzing the
response based on the flag settings chosen. Each operating system responds differently to these
special combinations. The tool includes presets for XMAS,NULL,FIN and ACK flag settings.