SYN scan is a popular port scanning technique used to identify open ports on a target system. This technique is based on the TCP three-way handshake, which is used to establish a connection between a client and a server. The SYN scan technique involves sending a SYN packet to each port on the target system and waiting for a response.
If a SYN-ACK packet is received in response to the SYN packet, the port is considered open, and the service running on that port is identified. If a RST packet is received in response to the SYN packet, the port is considered closed. If no response is received, the port is considered filtered or blocked by a firewall.
The SYN scan technique is fast and efficient and can be used to identify open ports and potential vulnerabilities on the target system. However, it may be detected by intrusion detection systems or firewalls, which can block or limit the number of SYN packets sent to a target system.
ACK scan is another port scanning technique that is based on the TCP three-way handshake. This technique involves sending an ACK packet to each port on the target system and waiting for a response.
If a RST packet is received in response to the ACK packet, the port is considered closed. If no response is received, the port is considered filtered or blocked by a firewall. If an unexpected response, such as a SYN-ACK packet, is received in response to the ACK packet, the port is considered open, and the service running on that port is identified.
The ACK scan technique is less commonly used than the SYN scan technique, but it can be useful in identifying open ports that are not detected by SYN scan or other port scanning techniques. However, it may be slower and less reliable than other scanning techniques and may also be detected by intrusion detection systems or firewalls.
FIN scan is a port scanning technique that involves sending a FIN packet to each port on the target system and waiting for a response.
If a RST packet is received in response to the FIN packet, the port is considered closed. If no response is received, the port is considered filtered or blocked by a firewall. If an unexpected response, such as a SYN-ACK or RST-ACK packet, is received in response to the FIN packet, the port is considered open, and the service running on that port is identified.
The FIN scan technique is less commonly used than SYN scan or ACK scan, but it can be useful in identifying open ports that are not detected by other scanning techniques. However, it may be slower and less reliable than other scanning techniques and may also be detected by intrusion detection systems or firewalls.
Xmas Tree Scan is a port scanning technique that involves sending a packet with the FIN, URG, and PSH flags set to each port on the target system and waiting for a response.
If a RST packet is received in response to the Xmas Tree packet, the port is considered closed. If no response is received, the port is considered filtered or blocked by a firewall. If an unexpected response, such as a SYN-ACK or RST-ACK packet, is received in response to the Xmas Tree packet, the port is considered open, and the service running on that port is identified.
The Xmas Tree Scan technique is less commonly used than other scanning techniques and may be less reliable, but it can be useful in identifying open ports that are not detected by other scanning techniques. However, it may also be detected by intrusion detection systems or firewalls.
Port scanning can be a useful tool for network administrators and security professionals, but it can also be used maliciously to identify vulnerabilities or exploit systems. To ensure that port scanning is conducted ethically and responsibly, it is important to follow best practices, including:
Port scanning is a valuable technique for identifying potential vulnerabilities and securing network systems. By understanding the different port scanning techniques, network administrators and security professionals can effectively identify open ports and services running on a target system, and take necessary steps to secure those systems. However, it is important to conduct port scanning ethically and responsibly and to follow best practices to avoid causing damage or disruption to the target system or network.
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