NMAP is a popular network scanning and sniffing tools is also a powerful tool for port scanning type safety assessment, is widely used in the security scan, NMAP is a useful online tool, also is often used in the production and development, mainly for port open view of detection and LAN information collection, etc., different Linux distributions generally also with NMAP package management tool, can also choose to go to the website to download the source code package compiled installation.

Install nmap

In case, you are unable to use nmap command, use below command to install it

 centos：yum install nmap
 ubuntu：apt-get install nmap  

Check that the installation is successful

 nmap -v

Nmap usage method

• Scan IP which common TCP port and UDP port are open

nmap 127.0.0.1 or nmap -sS -sU -p 1-65535 127.0.0.1

• Scan multiple IP addresses or subnet

nmap 127.0.0.1 172.16.6.1
nmap 172.16.6.1-100
nmap 172.16.6.0/24  

In the scan result, if the state column is open, it means the state is open; if it is filtered, it may be filtered by a firewall; if it is closed, it means the port is closed.

• Scans which hosts are alive in the subnet

nmap -n -sP 172.16.6.0/24

• Nmap route trace

namp –traceroute 8.8.8.8  

• Scans IP or subnet hosts for port

nmap -p 12598 127.0.0.1
nmap -p 12598 172.16.6.0/24

• An option that goes one step further and gives you more information about the services running on a specific host is ‘-A’.

nmap -A 127.0.0.1

• Nmap scans the operating system type using the -O option

nmap -O 12598 127.0.0.1

• For an in-depth understanding of the use of the nmap command, use it to examine the man pages

man nmap

Conclusions

nmap is one of those utilities that have so many options and capabilities, it can actually be overwhelming. As is the case with those types of utilities, you will end up using only a fraction of its capabilities to help get a specific job done. If you want to use it at its full potential, you’re in for a lot of trial and error and some hands-on experience with real networks.

So, you can read our post abour networks in this link.

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“fdisk” is such a tool that comes pre-installed on almost all the Linux distros. The tool works in the command line interface. Yet, it’s very simple and hassle-free. It’s a partitioning tool for HDDs, SSDs, USB thumb drives etc. Today, we’ll be checking out the usage of “fdisk”.

When you work with “fdisk”, it doesn’t immediately complete the operation. It holds the changes into memory and will perform the action only when you tell it to.

Identifying the “device identifier”

In the case of Linux, all the block devices or HDDs are identified by unique identifier names, for example, “sda”, “sdb” etc. Before proceeding, it’s important to make sure that you’re working on the right device. Otherwise, you may accidentally lose data from another device and find yourself in a mayhem of troubles.

Run the following command –

sudo lsblk

You can easily find out what device you’re about to modify. In my case, my 4GB USB flash drive is tagged as “sdb”.

Opening storage device with fdisk

For performing operations on a device, you have to lock it under fdisk. For that purpose, no partition of the device is allowed to be mounted.

From the above command, you can find out what partition was mounted.

Unmount the partition –

sudo umount /dev/sdb1

Now, it’s time to lock “sdb” under fdisk.

sudo fdisk /dev/sdb

“fdisk” usage

• Listing available partitions

Once the device is locked under fdisk, enter the following value –

p

You’ll be presented with a list of available partitions.

• Creating a new partition

A partition table is quite important as it holds the info about the partition(s) of the device. As of the time of publishing this article, there are a few available partition tables –

• DOS – One of the oldest partition tables developed by Microsoft. DOS partition table can’t hold more than 4 primary partitions. Highly suitable for small storage devices.
• GPT – A newly developed partition table that allows more than 4 primary partitions. Extremely useful for big storage devices like HDD, SSD etc.

If you wish to create a DOS partition table, enter the following value –

o

For a GPT partition table, use this value –

g

• Creating/removing partitions

If you want to delete a partition, enter this value –

d

Then, you’ll be asked for entering the partition number. Make sure to find out the list of partitions using the previous method.

For creating a new partition, enter the following value –

n

At first, you have to select the partition number. Hit “Enter” as the default value is always alright.

Now, you’ll be asked for the “First sector” number. Most of the cases, it’s also nothing to touch about (unless you’re sure what you’re doing). Just hit “Enter”.

Next, time to enter the size of the partition. For the partition size, it must not come up in fractions. For example, you want the partition size of 512MB, type “+512M” (without quotes). Similarly, for 2GB partition, the command will be “+1G”.

As you can see, the partition is created.

Another example –

• Finalizing all the modifications

After you’ve performed all the modifications, you can now finalize the real changes in your drive. Enter the following value –

w

The writing process is complete now but the partition(s) you created won’t be usable until you format them properly. Run the following command for formatting the partition in “ext3” format –

sudo mkfs.ext3 -L demoPartition /dev/sdb2

Here, “demoPartition” is the name of the partition. You can use any name as you like.

Now, the partition is ready for mounting. Run the following command –

sudo mount /dev/sdb1 /mnt

Verify the result –

df -h

Enjoy!

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If you don’t know how Meltdown and Spectre works, here’s a summary. Every modern processor uses a method called “speculative execution”. This method makes the processor function blazingly faster. Using the method, a hacker can execute such a program that can disclose sensitive info from other apps. Learn in-depth about the Meltdown and Spectre bug here.

For Windows users, there’s a tool called InSpectre. This tool will analyze your system and tell if you’re vulnerable to these bugs. Get InSpectre. However, for Linux users, this type of tool wasn’t available. Thankfully, Linux Lite developers created such a tool for every Linux distro. Linux Lite is a Linux distro based on Ubuntu.

How to use

The tool is very simple to use. It’s a CLI tool, so please be focused.

• Download the Spectre Meltdown Checker Automated from GitHub.
• Extract the ZIP archive in a folder.
• Open a terminal in that directory and run the following command:
• Double-click on “sm-start” or run the following command:

chmod +x sm-*

If you’re using XFCE with Thunar, use the following command:

xfconf-query --channel thunar --property /misc-exec-shell-scripts-by-default --create --type bool --set true

It’ll show an output like in the GIF shown below.

If this tool seems a bit difficult, there’s another similar tool. It’s a very simple, plain shell script to check out for the vulnerabilities. Get the script Spectre & Meltdown Checker. When you run the script, you can see the following result. It’s a sample one.

What to do now

After running this tool, you’ll know whether you’re vulnerable to any of the flaws. If you’re not, congratulations! In case your system is vulnerable, you need to think about it.

Whatever your system’s status is, it’s the best to run a system update. Different Linux distros follow different rules to manage and update the system. Here’s a detailed guide to update & upgrade your Linux.

Here’s a caution – don’t install Intel’s latest microcode. Different specialists are criticizing the buggy and troublesome patch from Intel. Many computers simply started reboot unexpectedly along with some other issues. So, for now, it’s the best to stay out of that microcode update.

For Linux users, Linux Lite can make a big change to your perspective and a refreshing desktop. It’s based on Ubuntu, the most popular Linux distro ever. It’s mostly focused on simplicity and faster performance. Check out Linux Lite today!

Have you checked your system? If not, do it now. The Meltdown and Spectre is a result of faulty processors, mostly Intel processors. These flaws can’t be removed completely without hardware replacement. However, using software upgrades, we can mitigate the danger.

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