Need help wuth understanding hese linuz commands if someone coould help me with

Question

Need help wuth understanding hese linuz commands if someone coould help me with these questions

1. Describe the function of denyhosts 2. How does Ncrack work? 3. What does sudo do? 4. What is a DOS attack? 5. What does the Linux command “grep-v grep" do? 6. When to use the tool ncrack? With ncrack, what does each of the following options mean? -v, --user, -P and -p 7. When to use htop on Linux? 8. When to use iotop on Linux? 9. What happens if you run the command :01: | : &}; : on a Ubuntu Linux system? 10. Explain the options -eaf for the Linux command ps

Explanation / Answer

1) Function of denyhosts : - It is a python scripts which analyses the ssh daemon server log messages in order to determine what hosts are trying to break into the system.

It is used to checks the targeted user accounts and even keep tracs of the number of attacks being performed.

2) Working of Ncrack: - It is a high-speed network authentication tool which is used to provide security to the companies’ network. Ncrack is similar functionality like Nmap. It is actually a dynamic engine which can be adapted based on network feedback. Protocol supported by Ncrack includes SSH, RDP, HTTPS, etc.

3) Sudo : it allows a normal user to run particular root commands if the user has permission to run those commands. By editing or making entry to the /etc/sudoers file, a user can run specific root commands.

4) DOS attack: - the Denial of Service is a kind of network attack, where attacks bring lots of unwanted traffic hitting the server making the server crash. Sometimes, it even crashes the whole network.

5) grep -v grep signifies that it does not include the usage of the grep command and display the output by eliminating the ‘grep’.

6) Ncrack : - it is an open source tool used for networking that are being used for network authentication cracking. It is being used while auditing large networks for checking weak passwords.

-p is used to apply the non-standard notational hosts.

-P specifies the password list used along with the path to the file.

--user specify the usernames directly used in the command line.

-v is used to increase the verbosity level.

7) htop: - htop shows the frequently updated list of all the processes that are running on the Linux machine, based on the amount of CPU usage by the processes.

8) iotop: - it actually displays the column of the Input/output usage details by displaying the table of existing I/O utilization by different processes.

9) Function() {..} : - Double bracket used for defining a function. And curly braces are used for the body of the function.

: | : is used to run the function within itself and the output is piped to another invocation.

& is used to run the command in the background.

; is used to separate two commands.

: indicates final command invocation and starts by running newly defined function.

10) ps command switches:

ps -eaf command gives output based on ‘e’ for active processes, ‘a’ for all processes and ‘f’ for full format listing.

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