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b lorenz

Welcome back, hope you are enjoying this series, I don't know about you but I'm enjoying it a lot. This is part 3 of the series and in this article we're going to learn some new commands. Let's get started

Command: w
Syntax: w
Function: This simple function is used to see who is currently logged in and what they are doing, that is, their processes.

Command: whoami
Syntax:   whoami
Function: This is another simple command which is used to print the user name associated with the current effective user ID.

Try it and it will show up your user name.

If you want to know information about a particular user no matter whether it is you or someone else there is a command for doing that as well.

Command: finger
Syntax: finger [option] [username]
Function: finger is a user information lookup program. The [] around the arguments means that these arguments are optional this convention is used everywhere in this whole series.

In order to find information about your current user you can simply type:

finger username

Here username is your current username.
To find information about root you can type:

finger root

and it will display info about root user.

Command: uname
Syntax: uname [options]
Function:   uname is used to display information about the system.

uname is mostly used with the flag -a, which means display all information like this:

uname -a

Command: df
Syntax: df [option] [FILE ...]
Function:   df is used to display the amount of space available.
If you type df in your terminal and then hit enter you'll see the used and available space of every drive currently mounted on the system. However the information is displayed in block-size, which is not so much human friendly. But don't worry we can have a human friendly output as well using df by typing:

df -h

the -h flag is used to display the used and available space in a more user friendly format.
We can also view the info of a single drive by specifying the drive name after df like this:

df -h /dev/sda2

That's it for now about df, let's move on.

Command: free
Syntax:   free [options]
Function: free is used to display the amount of free and used physical memory and swap memory in the system.
Again the displayed information is in block-size to get a more human readable format use the -h flag like this:

free -h

Command: cal
Syntax: cal [options]
Function: cal stands for calendar. It is used to display the calendar.

If you want to display current date on the calendar you can simply type:

cal

and wohooo! you get a nice looking calendar on screen with current date marked but what if you want to display calendar of a previous month well you can do that as well. Say you want to display calendar of Jan 2010, then you'll have to type:

cal -d 2010-01

Nice little handy tool, isn't it?

Command: file
Syntax: file filename ...
Function:   file is an awesome tool, it's used to classify a file. It is used to determine the file type.

Let's demonstrate the usage of this command by solving a Noob's CTF challenge using file and base64 commands. We'll talk about base64 command in a bit. Go to InfoSecInstitute CTF Website. What you need to do here is to save the broken image file on your local computer in your home directory. After saving the file open your terminal (if it isn't already). Move to your home directory and then check what type of file it is using the file command:

cd
file image.jpg

Shocking output? The file command has identified the above file as an ASCII text file which means the above file is not an image file rather it is a text file now it's time to see it's contents so we'll type:

cat image.jpg

What is that? It's some kind of gibberish. Well it's base64 encoded text. We need to decode it. Let's learn how to do that.

Command: base64
Syntax:   base64 [option] FILE ...
Function: base64 command is used to encode/decode data and then print it to stdout.

If we're to encode some text in base64 format we'd simply type base64 hit enter and then start typing the text in the terminal after you're done hit enter again and then press CTRL+D like this:

base64
some text here
<CTRL+D>
c29tZSB0ZXh0IGhlcmUK # output - the encoded string

But in the above CTF we've got base64 encoded data we need to decode it, how are we going to do that? It's simple:

base64 -d image.jpg

There you go you've captured the flag.
The -d flag here specifies that we want to decode instead of encode and after it is the name of file we want to decode.

Voila!
So now you're officially a Hacker! Sorry no certificates available here :)

That's it for this article meet ya soon in the upcoming article.

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b lorenz

Nmap is a free utility tool for network discovery, port scanning and security auditing, even though we can use it for more than that but in this article we will learn how to do these three things with nmap.

The original author of nmap is Gordon Lyon (Fyodor). Nmap is licensed under GPL v2 and has available ports in many different languages. Nmap is available for Linux, Windows, and Mac OS X. You can download your copy of nmap from their website.

Lets get started with nmap.

When performing pentests we always look for networks we are going to attack. We need to identify live hosts on the network so that we can attack them. There are plenty of tools available for finding live hosts on a network but nmap is one of the best tools for doing this job.

Lets start with simple host (target) discovery scans i,e scans that will tell us which ip address is up on our target network. Those ip addresses which are up on our target network are the ones that are assigned to a device connected on our target network. Every device on the network is going to have a unique ip address.
To perform a simple host discovery scan we use the following command

nmap -v -sn 10.10.10.0/24

flags we used in the above command are
-v for verbose output
-sn to disable port scan (we don't want to scan for ports right now)

Following the flags is the ip address of the target network on which we want to look for live hosts. The /24 at the end of the ip address is the CIDR that specifies the subnet of the network on which we are looking for live hosts.

After running the above command you should get a list of live hosts on your target network.
If you just want to know the list of ip addresses your command is going to scan, you can use the -sL flag of the nmap like this.

nmap -sL 10.10.10.0/24

this command will simply output the list of ip addresses to scan.

We sometimes want to do dns resolution (resolving ip addresses to domain names) when performing our network scans and sometimes we don't want dns resolution. While performing a host discovery scan with nmap if we want to perform dns resolution we use -R flag in our command like this:

nmap -v -sn -R 10.10.10.0/24

And if we don't want to perform dns resolution of hosts during our scan we add the -n flag to our command like this:

nmap -v -sn -n 10.10.10.0/24

After we have discovered the hosts that are up on our target network, we usually put the ip addresses of these hosts into a file for further enumeration.

Next step in our enumeration would be to detect which operating system and which ports are running on these live hosts, for that we run this command:

nmap -O -v 10.10.10.119

here we use -O (capital o not zero) for operating system detection and by default nmap performs SYN Scan for port discovery. However nmap scans for 1000 ports only by default of a particular host.

To make nmap go over a list of ip addresses in a file we use -iL flag like this:

nmap -O -v -iL targetlist

where targetlist is the name of the file which contains ip addresses that we want to perform port scan on.

To make nmap scan all the ports of a target we use the -p flag like this:

nmap -p- -v 10.10.10.121

We can also specify a range of ports using the -p flag like this:

nmap -p1-500 -v 10.10.10.121

here 1-500 means scan all the ports from 1 to 500.

We can use a number of scan techniques to discover open ports on our network but I will only discuss some of them for brevity.

We can perform a TCP SYN scan using nmap with -sS flag like this:

nmap -sS -v 10.10.10.150

We have also flags for TCP connect and ACK scans which are -sT -sA

nmap -sT -v 10.10.10.150

nmap -sA -v 10.10.10.150

We can also perform UDP scan as well instead of TCP scan using -sU flag

nmap -sU -v 10.10.10.150

We can perform TCP Null, FIN, and Xmas scans using the flags -sN, -sF, -sX

nmap -sN -v 10.10.10.150

nmap -sF -v 10.10.10.150

nmap -sX -v 10.10.10.150

If you don't know what these scans are then please visit Port Scanning Techniques and Algorithms for explanation.

After discovering the open ports on our target host, we want to enumerate what services are running on those open ports. To enumerate services and versions information on open ports we use the -sV flag like this:

nmap -sV -v 10.10.10.118

This should give us information about what services are running on what ports and what versions of those services are running on the target host.

nmap has an interesting feature called NSE nmap scripting engine. It allows users to write their own scripts, using the Lua programming language, to automate a wide variety of networking tasks. nmap ships with a diverse set of scripts which are very helpful to enumerate a target. To use the nmap default set of scripts while enumerating the target, we use the -sC flag like this:

nmap -sC -sV -v 10.10.10.118

We can also save the results of our nmap scans to a file using the -o flag like this

nmap -sC -sV -v -oA defaultscan 10.10.10.119

here -oA tells the nmap to output results in the three major formats at once and defaultscan is the name of the file that will be prepended to all the three output files.

This is the end of this short tutorial see you next time.

References:
https://nmap.org/book/scan-methods-null-fin-xmas-scan.html

What is Peer to Peer (P2P) network?

As when devices are connected with each other for the sake of communication that'll be known as a Network. Now what is peer to peer network? In P2P network each and every device is behaving like a server and a client as well. Moreover They are directly connected with each other in such a way that they can send and received data to other devices at the same time and there is no need of any central server in between them.

There is a question that mostly comes up into our minds that Is it possible to capture data from the network? So the answer is yes. We can easily captured data from the network with the help of tools that have been created for network troubleshooting, so whenever there will be some issues happening to the network so we fixed that issues with the help of tools. Most usable tool for data capturing that every network analyst used named Wireshark but there are so many other tools available over the internet like SmartSniff, Ethereal, Colasoft Capsa Network Analyze, URL Helper, SoftX HTTP Debugger and many more.

What is Wireshark?

Wireshark is an open source network analyzer or sniffer used to capture packets from the network and tries to display the brief information about the packets. It is also used for software and communication protocol development. Moreover, Wireshark is the best tool to intercept the traffic over the network.

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Monday, August 31, 2020

Linux Command Line Hackery Series - Part 3

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Sunday, August 30, 2020

Nmap: Getting Started Guide

Related links

Networking | Routing And Switching | Tutorial 2 | 2018

What is Peer to Peer (P2P) network?

What is Wireshark?