Network Address Translation (NAT) translate internet address to private address. Because there are limited number of internet TCP/IP addresses, so many devices on the private network can use only one access point to connect to the internet. In this is setting, all the devices will have a single public IP address and usually the router will have the function of the NAT and translate the same public IP address to unique private IP address.
A firewall is a protection form the internet which may have some unnecessary request to connect or communicate to our device amount our network.
Firewall provided security device service to monitor the network communication between internal network and external network (normally is outside, such as internet). In the previous version firewall, called stateless firewall, it protects the networks connection base on the actually destination where the data going to. It checks the information base on the filtering rule which match the destination or context and perform the action, for example blocking the connection. If the filtering rule do not match, there are not action will be taken for preventing any attack. So, stateless firewalls is consider as less rigourse
Another firewall is stateful firewall which will monitor the stat of the connection amount the network. Base on the context, the firewall will analysis the packet and traffic to apply the filtering rules. Like the handshake process, if the outside only request the handshake but not complete the request, the request will be filtered out.
Application firewall is a more complex way to filter protect out system by actually investigate the detail of the conversation. It distinguishes the type of connection/ traffic, such as a web type traffic only communicate from the source and the destination. Compare other traffic like malicious traffic have a complete different patent.
Secure Shell is a protocol for sending data for one computer to another computer in a secure way. There several similar protocols doing the same thing such as telnet and FTP but the different between ssh with other is that SSH is secure. Because other protocol sending data through internet without any encryption of the data, so if you are entering password or any importing information, they will send it in plaintext over the internet and could be stolen by the other and get your password. SSH can secure the connection to reduce the risk of your password being stolen.
First step of using SSH is install the software and setup a proper firewall to make sure can be establish.
The normal setting of SSH is using port 22, but it is to comment to recognize, some people may use 2222 or 12222 to protect the connection. After the setup process, setup account in both computer and setup the connection by just inputting the username and password.
The first amazing thing SSH can do is knowing what program is running on the other computer,(the one we have connected with) and try to kill it. For example a calculator programm is running on the another computer and we would like to kill it. We can search what is running on the computer by command like this: ps aux | grep calc
It grep all the information of tool names with ‘calc’ and we can also know the process ID which we need to know for killing it by using command:
Kill -9 XXXX
It will kill the program by using SSH.
Another function of using SSH is transferring data form one computer to another computer. The data could be an entire file you need to send or transferring command line to control another form another place in different platform. There are sever different SSH client and server available in different such as Linux and windows.
Reference:
NAT Firewall
openssh in linux
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