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Network Hacking

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									~: Network Hacking :~

Network Hacking is generally means gathering information about domain by using tools like Telnet, NslookUp, Ping, Tracert, Netstat, etc. It also includes port scaning and port surfing using various tools.

Ping :- Ping is part of ICMP (Internet Control Message Protocol) which is used to
troubleshoot TCP/IP networks. So, Ping is basically a command that allows you to check whether the host is alive or not. To ping a particular host the syntax is (at command prompt)-c:/>ping example:- c:/>ping

various attributes used with ping command and their usage can be viewed by just typing c:/>ping at the command prompt.

Netstat :- It displays protocol statistics and current TCP/IP network

connections. i.e. local address, remote address, port number, etc. It's syntax is(at command prompt)-c:/>netstat -n

Telnet :- Telnet is a program which runs on TCP/IP. Using it we can connect to
the remote computer on particular port. When connected it grabs the daemon running on that port. The basic syntax of Telnet is (at command prompt)-c:/>telnet By default telnet connects to port 23 of remote computer. So, the complete syntax isc:/>telnet port example:- c:/>telnet 21 or c:/>telnet 21

Tracert :- It is used to trace out the route taken by the certain information i.e.
data packets from source to destination. It's syntax is (at command prompt)-c:/>tracert example:- c:/>tracert

Here "* * * Request timed out." indicates that firewall installed on that system block the request and hence we can't obtain it's IP address. various attributes used with tracert command and their usage can be viewed by just typing c:/>tracert at the command prompt. The information obtained by using tracert command can be further used to find out exact operating system running on target system.

Port Scanning :- Port scanning is carried out to determine a list of open ports
on the remote host that have certain services or daemons running. In port scanning, the attacker connects to various TCP and UDP ports and tries to determine which ports are in listening mode.

1) TCP Ports Scanning :- Almost all port scans are based on the client sending a packet containing a particular flag to the target port of the remote system to determine whether the port is open. Following table lists the type of flags a TCP packet header can contain. Meaning This flag tells the receiver that the data pointed at by URG (urgent) the urgent pointer required urgently. This flag is turned on whenever sender wants to ACK acknowledge the receipt of all data send by the (acknowledgment) receiving end. The data must be passed on to the application as PSH (push) soon as possible. RST (reset) There has been a problem with the connection and Flag

one wants to reset the connection with another. If system X wants to establish TCP connection with system Y, then it sends it's own sequence number to SYN (synchronize) Y, requesting that a connection be established. Such apacket is known as synchronize sequence numbers or SYN packet. If system X has finished sending all data packets and wants to end the TCP/IP connection that it has FIN (finish) established with Y, then it sends a packet with a FIN flag to system Y. A typical TCP/IP three way handshake can be described as follows : 1) The client sends a SYN packet to the server. 2) The server replies with a SYN packet and acknowledges the client's SYN packet by sending an ACK packet. 3) The client acknowledges the SYN sent by the server. Different techniques of TCP port scanning are :1) TCP connect port scanning 2) TCP SYN scanning (half open scanning) 3) SYN/ACK scanning 4) TCP FIN scanning 5) TCP NULL scanning 6) TCP Xmas tree scanning 2) UDP Ports Scanning :- In UDP port scanning, aUDP packet is sent to each port on the target host one by one. If the remote port is closed, then the server replies with a Port Unreachable ICMP error message. If the port is open then no such error message is generated. 3) FTP Bounce Port Scanning :- The FTP bounce port scanning technique was discovered by Hobbit. He revealed a very interesting loophole in the FTP protocol that allowed users connected to the FTP service of a particular system to connect to any port of another system. This loophole allows anonymous port scanning. Recommended Tools Nmap Superscan

O.S. Fingerprinting :- O.S. Fingerprinting refers to detection of target
computer's operating system.

Since, different operating system responds differently to the same kind of ICMP message, it is very important for an attacker to determine the exact operating system running on target system. Also attacker can carry out attacks by taking over the vulnerabilities/bugs found in that particular operating system. There are four areas that we will look at to determine the operating system (however there are other signatures that can be used). These signatures are: 1) TTL - What the operating system sets the Time To Live on the outbound packet. 2) Window Size - What the operating system sets the Window Size at. 3) DF - Does the operating system set the Don't Fragment bit. 4) TOS - Does the operating system set the Type of Service, and if so, at what. There are two different types of O.S. Fingerprinting technique 1) Active O.S. Fingerprinting :- Remote active operating system fingerprinting is the process of actively determining a targeted network node’s underlying operating system by probing the targeted system with several packets and examining the response(s), or lack thereof, received? The traditional approach is to examine the TCP/IP stack behavior (IP, TCP, UDP, and ICMP protocols) of a targeted network element when probed with several legitimate and/or malformed packets. Recommended Tools


2) Passive O.S. Fingerprinting :-Passive fingerprinting is based on sniffer traces from the remote system. Instead of actively querying the remote system, all you need to do is capture packets sent from the remote system. Based on the sniffer traces of these packets, you can determine the operating system of the remote host. Just like in active fingerprinting, passive fingerprinting is based on the principle that every operating system's IP stack has its own idiosyncrasies. By analyzing sniffer traces and identifying these differences, you may be able determine the operating system of the remote host. Recommended Tools

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