If a hacker wants to perform ICMP (Internet Control Message Protocol) scanning, it can be done manually. I this case, the computer should have to be connected to the internet. It is the proactive identification of the system's vulnerabilities within a network in an automated manner to determine whether the system can be exploited or threatened. This scan is also used to check the target's/victim's filtering system. The RST packet signifies whether the port is open or closed.

ACK Flag Probe Scan: Here, the attacker sends TCP probe packets where an ACK flag is set to a remote device, analyzing the header information (TTL and WINDOW field).

If there is no response, it indicates that the port is open, and RST means it is closed.

Inverse TCP Flag Scan: Here, the attacker sends TCP probe packets with a TCP flag (FIN, URG PSH) or no flags.

Depending on the response of the scan, the port is determined, whether open or closed.

IDLEScan: An IDLE scan uses a spoofed/hoax IP to send the SYN packet to the target by determining the port scan response and IP header sequence number.

FIN scan receives the same response and has the same limitations as XMAS scans.

FINScan: A FIN scan is similar to an XMAS scan except that it sends a packet with just theВ FINВ (finish) flag and no URG or PSH flags.

If there is an open port, there will be no response but the target responds with an RST/ACK packet if the port is closed.

XMASScan: XMAS scan send a packet which contains URG (urgent), FIN (finish) and PSH (push) flags.

If an RST is retrieved from the target, it is assumed that the port is closed or not activated.В SYN stealth scan is advantageous because a few IDS systems log this as an attack or connection attempt. A hacker sends an SYN packet to the victim, and if an SYN/ACK frame is received back, then the target would complete the connection, and the port is in a position to listen.

SYNScan: SYN scan or stealth doesn't complete the TCP three-way handshake technique.

ACK denotes acknowledgment, which is used to establish a connection between two hosts. Here SYN denotes synchronization, which is used to initialize connections between the client and the server in packets. The client again responds to the server by sending an ack packet. Here first, the client sends a synchronization packet for establishing a connection, and the server listens to and responds with a syn/ack packet to the client.

Here, TCP (Transmission Control Protocol) and IP (Internet Protocol) are the two protocols used for handshaking between a client and a server. In computer terms, handshaking means the automated process used to set dynamic parameters of a communication channel between two entities using some protocols. TCP/IP HandshakeД«efore moving to the scanning techniques, we have to understand the 3-way TCP/IP handshaking process. Once the Hacker fetches the victim organization's IP address by scanning TCP and UDP ports, the Hacker maps this organization's network under his/her grab.

During this scan, hackers need to find out those live hosts, firewalls installed, operating systems used, different devices attached to the system, and the targeted organization's topology. It is a conventional technique used by penetration testers and hackers to search for open doors from which hackers can access any organization's system. This information may be used by intruders/hackers to portray the lists of applicable exploits. Telnet and ID Serve are the tools used mainly to perform a Banner-grabbing attack. Banner Grabbing: is the method for obtaining information regarding the targeted system on a network and services running on its open ports.Scanning beyond IDS (Intrusion Detection System).Check for open ports (The technique is called Port Scanning, which will be discussed below).Hackers and Pen-testers check for Live systems.To discover and deal with vulnerabilities in Live hosts.To discover the Operating System and system architecture of the target.To discover services that are running on a host computer.To discover live hosts/computer, IP address, and open ports of the victim.Vulnerability Scanning Objectives of Network Scanning.

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