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Show Failed SSH Login Attempts

Today’s article is pretty straightforward, I’m going to show you how to show failed SSH login attempts. It should be a pretty short article, as I’m just going to show you two ways for a couple of system types. This is Linux, so there are certainly more ways to go about it, but I’ll show you a couple of them.

Yes, I’ve written about SSH a great deal. It is, in my opinion, one of the greatest remote administration tools ever conceived. But, attackers know this and any public-facing computer, with an IP address that can be reached externally, will be subject to port scanning and intrusion attempts.

I’ve written some SSH security articles, but one of the best things you can do is change the port that SSH uses. This will stop a bunch of malicious intrusion attempts. However, smart hackers will quickly scan for open ports with automated tools. Some of them will inevitably find your SSH port.

These people will then try to login. Securing your SSH is pretty important. I’ve written a few articles, so here’s a search of SSH-related articles previously published. Feel free to browse them at your leisure. I really need to do an article about Fail2Ban, but I haven’t gotten that far yet. One of these days!

So, like I said, you can show failed SSH login attempts. One of the things you can do with this information is scan for commonalities. You can also check to see if the hackers are using a username that already exists. If they’re using a username that already exists, it could be coincidental or it could mean they already have some insider information.

Well then, let’s jump into the article…

Show Failed SSH Login Attempts:

Like oh so many of my articles, and this one involving SSH, you’re going to want an open terminal for this. If you don’t know how to open the terminal, you can do so with your keyboard – just press CTRL + ALT + T and your default terminal should open.

By the way, if you’re this far into the article and don’t know what SSH, it’s ‘secure shell’ and a way to remotely connect to another computer. Basically, you login to a remote computer and then you’re using the remote computer’s terminal. However, you can do so with graphics, you just need to forward x11.

So, it’s a pretty useful tool. I use SSH often, even in my own home. What? It’s faster than walking to another room, and I often test things remotely. SSH makes perfect sense for this sort of stuff.

With your terminal freshly open and properly logged into the remote computer, you can show failed SSH login attempts pretty easily. Like I said, I’ll show you a couple of ways. The first is pretty universal and should work with all but a couple distros:

grep "Failed password" /var/log/auth.log

1	grep "Failed password" /var/log/auth.log

RHEL and CentOS (Fedora too? I have not tested.) may store the data elsewhere, so you can try this command to show failed SSH login attempts:

grep "Failed" /var/log/secure

1	grep "Failed" /var/log/secure

If you have failed SSH login attempts, one of those two commands should show you them. If the first doesn’t work, and you know you have failed attempts, try the second one. The logs are usually stored (as far as I know) in either of those two locations.

Closure:

See? It’s a nice and short article today, just like I said it would be. This time around, we’ve learned how to show failed SSH login attempts. Even if you’re using Fail2Ban and mandating certificate login, it’s always good to check to see what the bad guys are up to.

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How To: Check For Bad Sectors On Your Disks

Today, we’re going to examine one way to check for bad sectors on your disks. Once again, it won’t be a particularly taxing article, but it’s something everyone should know how to do. This being Linux, I’m sure there are alternative tools.

Hard drives, from spinning platter to solid-state, are divided into sectors. Sometimes, these sectors go bad. The disk’s software manages this to some extent, and actually has more space available than listed so that it can make up for bad sectors as time passes.

But, you still get bad sectors. It’s just the nature of the game, and no disk drive is immune to this. All you can do is accept them and, in some cases, repair them.

See, there are two types of bad sectors. The first is a hard bad sector, which is hardware related and can’t be fixed. The second is a soft bad sector, which is a software issue and it can be fixed. I’ll someday write an article about how to fix soft bad sectors, but I won’t bother getting into that today.

With all that in mind, the tool we’ll be using is appropriately named ‘badblocks’, which describes itself thus:

badblocks – search a device for bad blocks

Badblocks has a variety of uses, so you can always get a head start on this article by reading the man page.

man badblocks

1	man badblocks

So, with that already covered, let’s just jump into the article.

Check For Bad Sectors:

This article requires an open terminal, like many other articles on this site. If you don’t know how to open the terminal, you can do so with your keyboard – just press CTRL + ALT + T and your default terminal should open.

With your terminal now open, you should probably identify your drives with the following command:

sudo fdisk -l

1	sudo fdisk -l

The output of this may look a bit like this:

You can see your drive’s identification with the output of fdisk -l.

As you can see, it’s listed as /dev/<device_ID> and that’s the information you want to hold onto.

Sometimes, it’s a lot more complicated, and will look something like this:

As you can see, they’re all start with ‘dev/sd*‘ and end up as /dev/<device_ID>. The system I ran badblocks on is quite a bit more complicated than the output from the laptop I used in the first instance.

Now, you want to scan your individual device to check the for bad sectors. That’s actually just a simple command. You can use:

sudo badblocks -v /dev/<device_ID>

1	sudo badblocks -v /dev/<device_ID>

The -v ensures the output is verbose and sent to the screen. You can also write that data to a text file for reference. To do that, you just use a command similar to this:

sudo badblocks -v /dev/<device_ID> > badblocks.txt

1	sudo badblocks -v /dev/<device_ID> > badblocks.txt

Then, you’ll have a badblock.txt file you can refer to, showing you information about any bad blocks. I wanted to show you the output from a disk with bad blocks, but I don’t appear to have any to show you. I tried quite a few, but it was a no-go. Ah well… You’ll figure it out easily enough. It’s not even a little hard to check for bad sectors!

Closure:

Yup… You have another article. This time you learned how to check for bad sectors, a pretty handy tool – especially if you’re finding corrupt files on your disks. If you are facing corrupt files, this would be the first step I’d suggest taking.

Anyhow, the show does go on and you got a new article. I am more or less feeling just fine now, just some lethargy and not a whole lot of energy. Sweet!

How To: Check Disk Usage With ‘df’

In today’s article, we’re going to do exactly what the title suggests; we’re going to check disk usage with ‘df’. This means we’ll be checking disk usage in the terminal. Seeing as ‘df’ is included with every distro on the planet (I’m pretty sure) it means this won’t be all that complicated.

I am still a bit under the weather, but the show must go on! I’ve gone this long without missing a publication date, so I might just as well keep the streak up.

As the title suggests, we’ll be using ‘df’ to check disk usage. This will already be installed as one of the default tools, so you won’t need to install it. That’ll save some time! If you’re curious, the ‘df’ tool describes itself as:

df – report file system disk space usage

If you want to get a head start, you can check the help page. To do that, you’ll want to run:

dh --help

dh --help

If you’re like to check the version, the command is:

df --version

1	df --version

So, with that in mind, let’s just jump into the article.

Check Disk Usage With ‘df’:

Obviously, this is yet another article where we’re learning about doing things in the terminal. That means you’ll need an open terminal. If you don’t know how to open the terminal, you can do so with your keyboard – just press CTRL + ALT + T and your default terminal should open.

With your terminal now open, you can just run the command by itself:

df

In some cases, it will throw an error and not be able to read everything. That’s usually easily resolved. Just run the command as a privileged user. So that would look like:

sudo df

sudo df

Now, you can use that output to do a bunch of math, or just pay attention to the percentages. Or, if you’re wanting, you can use the -h flag and get the output in human-readable format. That looks like:

sudo df -h

1	sudo df -h

The output of which might look a little something like this:

the output of sudo df -h — See? No errors and it is nice and readable! You can’t go wrong with that!

As you can see in the picture, I’m only using less than half of my available disk space. I don’t need to worry about running out of space any time soon, but if it gets low I can always check disk usage with ‘df’. Also, it doesn’t matter what directory you’re in when you run the command. As you can see, it runs just fine while in the Downloads directory.

I also wrote an article about using GUI methods to visualize disk space usage. You might prefer one of those methods, but you can always just use the terminal to check disk space.

Closure:

It seemed like a good idea to do a quick article tonight. I’m watching IMSA’s last race of the season and feeling poorly, so hopefully I get some sleep at a reasonable hour. Still, as I mentioned, the show must go on. The site has had a new article every other day for quite a while. I might as well keep up the schedule.

How To: Go To A Specific Line In Nano

In today’s article, we’re going to learn how you can go to a specific line in Nano. It’ll be an easy article, perhaps even a fairly brief article. There are a just a couple of ways to cover, so it won’t take all that much time or space.

Often, when things like scripts throw an error, they’ll tell you on which line number the error happened. There are often hundreds or thousands of lines in complicated files and navigating to the correct line number is tedious, prone to error.

You can be pressing the down arrow for quite a while! So, why not note the line number where the error occurred and open the file at that specific line? It’s perfectly good sense! It’s such good sense that I figured I’d write an article about it.

You all know that I’m a Nano fan. You can read the ‘big’ Nano article here. If that’s not enough, this link is to a search for Nano across the entire site. There are nearly 30 articles that use Nano in them. I really am quite a fan.

Why am I a fan? Well, the first link will probably tell you that, but I like it because it’s simple. Nano’s starting to be fairly universal. It’s light and that’s why I like it – it’s only meant for quick text file edits.

Nano’s not really the right tool for writing a book, nor would I want to use it to write large scripts or for programming. For what it is, it’s great. If it’s not great, odds are good that you’re not using it as the tool it is. Sure, it’ll work for other things, but it excels at being what it is – a quick text editor in the terminal.

Go To A Specific Line In Nano:

Nano is a terminal-based tool. So, you obviously need to have an open terminal. If you don’t know how to open the terminal, you can do so with your keyboard – just press CTRL + ALT + T and your default terminal should open. Tada! (That’s mostly copy/paste from previous articles, but I do sometimes mix it up a little!)

With your terminal open, let’s show you how to go to a specific line in Nano. It’s pretty easy, and we’re going to use a file most users will have. If you don’t have a ~/.bash_history file, you can use any plain text file you want.

I suppose we should first make sure that you have Nano installed. To check, you can just look for the version. That’s done with:

nano -V

nano -V

Your output should look something like:

If Nano isn’t installed, and you’re using any mainstream distro, it’s certainly in your default repositories. You can install it like you would any other piece of software in the repositories.

Now, there are two ways to open and go to a specific line in Nano. The first is probably the easiest. Using our ~/.bash_history as an example, the command looks like this:

nano +25 ~/.bash_history

1	nano +25 ~/.bash_history

Where you see the +25 flag, that’s the place where you specify the line number to start with when you open Nano. You can use any number you want, provided there are that many lines in the file you’re intending to edit.

The next way is also easy. Using your keyboard, press CTRL + Shift + –. Nano will then present you with the chance to enter in a specific line. It looks like a lot like this:

open a specific line in nano — See? Follow the arrow and that’s where it prompts you to enter a line number. ‘Snot hard at all!

So, now you have two ways to go to a specific line in Nano. I told you that it was going to be easy! Nano is awesome.

Closure:

There’s another article! It’s on one of my favorite subjects – Nano. Now you’ve learned how to go to a specific line in Nano, which is a pretty handy trick to have in your toolbox. It can save you all sorts of time, and not just time scrolling. It means you aren’t paying attention to the rest of the fluff and you can concentrate better, or so it seems to me. For what it is, Nano is my favorite plain text editor and it’s remarkably useful at times.

Compress A File With WinRAR

Today’s article is going to teach you how to compress a file with WinRAR. This isn’t exactly something you’re going to do often, unless you share files with Windows users. If you do share files with Windows users, this isn’t such a terrible idea. There are worse ideas, some of which are on this site.

Before you get to excited, there are countless ways to compress a file in Linux. The odds of you technically needing WinRAR are about zero. Still, that doesn’t mean we can’t have fun and learn new things!

Right?

Right!

It’s great to learn new things, even if you’re never gonna use them. Until about 5 minutes ago, I can’t remember the last time I felt the urge to compress a file with WinRAR. I’ve previously written about WinRAR, actually.

How To: Extract An .rar File

So, if you follow that link you’ll learn how to perform the other end of this operation! I’d like to pretend I planned it that way, but I did not. No, there’s no rhyme or reason to the publication schedule – except you get a new article every other day.

Compress A File With WinRAR:

Yup. You’re gonna need an open terminal for this one. If you don’t know how to open the terminal, you can do so with your keyboard – just press CTRL + ALT + T and your default terminal should open.

First, you’re going to need rar. It’s probably in your default repositories. It’s there for Debian, Ubuntu, and Mint. So, it’s probably available for you. You can get the proprietary version of WinRAR here. (Or not… I don’t see a whole lot of folks wanting that, but it’s there if you do! Also, I think it’s just a trial version.) Or, install it from your repositories. With those operating systems, it’s just:

sudo apt install rar

1	sudo apt install rar

Now, it’s really easy to compress a file with WinRAR. The command is:

rar a <compressed_file_name>.rar <file_or_folder_name>

1	rar a <compressed_file_name>.rar <file_or_folder_name>

The ‘a’ flag is telling the command to archive the file/folder you named. If you wanted to compress a file (or even a directory) named foo, it’d look like this:

rar a foo.rar foo

1	rar a foo.rar foo

See? That’s all you really needed to know if you want to compress a file with WinRAR. It’s not exactly complicated, but it’s helpful to know how if you come across a situation where you actually need to know. Again, there’s a zillion ways to compress files in Linux, so you’re not going to need this one all that often unless you really need it. If you do use WinRAR with Linux often, please leave a comment explaining why.

Closure:

Yup. It’s another article! This one teaches you how to compress a file with WinRAR. In my defense, this is information that’s from my notes. I have a whole lot of notes, but this one stood out today and so you get this for your article. You’re welcome!