Tag: remote access

Disallow SSH Login For A Specific User

In today’s article, we’re going to learn how to disallow SSH login for a specific user. The reasons you might want to do this should be obvious, so that’ll save some time! Read on to learn how!

I’ve covered SSH in many articles. If you search for “SSH”, you’ll find a bunch of articles covering the subject. I’m not sure why there are so many, but there are. I seem to have a lot of notes on the subject. 

Here, this link will help you search for SSH articles.

SSH is “Secure Shell”, a method to login to remote computers so that you can manage them without being their physically. It’s used by systems administrators regularly, without ever needing a GUI to manage their Linux systems.

It’s also used by people like me, too lazy to walk to the other side of the room. I’m literally using SSH to manage stuff on my laptop from here on this desktop as I write this. On top of that, while not logged in right now, I was using SSH to manage a VPS earlier today.

So, SSH isn’t just for professional system administrators and, if you use SSH at home, you might as well know how to secure it. This article will help you secure your system – by learning how to disallow SSH login for a specific user.

Disallow SSH Login For A Specific User:

This article requires an open terminal on (and connection to) the computer you wish to change. That may require you to login to that computer remotely. If you’re on a local device and 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. Otherwise, SSH into it like a boss.

With your terminal/connection now open, enter the following command:

Find a place to make a new line and enter the following with some care:

Now, this one is a bit picky. Obviously, you substitute <username> with the real name – but in between “DenyUsers” and the username you absolutely MUST press the TAB key. If you try to just use spaces, it will not work! You MUST use the TAB key which will appear to insert spaces for you!

Assuming you’ve done everything correctly, you’ll need to restart SSH for the changes to take effect. You can do that with this command:

If you were logged into a remote system to make the changes on that system, the above command is gonna log you out and you’ll need to login again. You knew that, but I figure I’ll mention it.

Hmm… If you’re a barbarian that doesn’t use systemd, try this:

When SSH restarts, the prohibited user will get a “Permission Denied” message when they try to login. Ha! That’ll teach Jerry in accounting from thinking he’s a system admin!

Closure:

Whelp… You have another article. This one has shown you how to disable SSH login for a specific user (Jerry in accounting, who had no business accessing the server anyhow). You’re welcome!

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TeamViewer; My Most-Recent Favorite Alternative To VNC.

Today’s article is going to be about my latest favorite VNC alternative, TeamViewer. It’s a surprisingly handy application that just works. Read on to learn more about it!

I’m a pretty big fan of VNC (Virtual Network Computing, from RealVNC). Actually, it’d be a bit more accurate to say that I’m a pretty big fan of remotely managing devices. Among the ways I do this, VNC is a nice way to do so graphically.

Basically, remote administration software such as this forwards the remote desktop to a window on my local desktop and allows me the control as though I was physically seated at the device. I have quite a few devices, and remotely manage the majority of them. I have computers in my house that I seldom physically use, I manage them all remotely. 

SSH is often adequate for anything I want to do, but not always. I can even forward SSH but not all applications work well with that. Sometimes I just want a GUI, as some things are best done in a GUI.

Besides, TeamViewer is free for personal use, and I like TeamViewer because it just works, even over the world wide web without knowing an IP address. I can use it to help friends and relatives by just talking to them long enough to get started.

Frankly, VNC can be a pain in the butt to configure and my favorite VNC client (RealVNC) is proprietary. So, using the proprietary TeamViewer doesn’t bother me. 

If you insist on opensource, this isn’t the tool for you. If you want something that is easy and just works, read on:

Getting and Using TeamViewer:

I’ll explain how to install it with Debian/Ubuntu/etc, but you can easily install TeamViewer for other Linux package management systems. Start by opening your terminal by pressing CTRL + ALT + T.

Once open, let’s grab the latest .deb with wget and install it. If you don’t have wget installed, you can do that with sudo apt install wget and then proceed with:

Copy and paste all three of those lines individually, of course. Press ENTER after each one. The last command should complete the process and would normally be the last step but this is proprietary software so you’ll need to run TeamViewer at least once in order to accept the license agreement. You can just do that in the terminal with:

That should pop up a window where can accept the license and keep on trucking.

Now, you’ll have to install TeamViewer on each device you want to manage and it’ll need to be installed on any device you wish to use to control the rest. Just be careful and read the prompts. It installs and works like a champ.

You’ll need to configure it on each device as well, allowing remote connections and setting up passwords as needed. It can check a centralized server, so the host doesn’t need to know things like ports and passwords.

It’s easily configured the first time, and once you’re done it a remote connection will hopefully look a bit like this:

TeamViewer in action.
This is what a connection might look like. It’s what mine looks like at this minute in time.

You can use this as a single instance or you can configure an account online with the management console to keep track of all your connections from a single point. You’ll spend a confusing amount of time making your browsers and devices ‘trusted’ status. All of this, of course, has obvious privacy implications.

Privacy & Security Concerns:

Again, they’re absolutely going to track your usage. They’ll know your IP addresses and the names of the devices you’re connecting to. They will know when you connect, how long you stay connected, and more. On top of that, they’ll know your email address, if you give it to them.

Having used them for a while, I see no spam from them and they’ve been nothing but acceptably and professionally behaved from my perspective. I don’t even get any regular newsletter emails from them. I think it’s safe to assume they’re currently not doing so. They do a whole lot of email verification steps if you want to trust devices.

Being proprietary, we have no idea what the source code looks like. We have no way to be sure that they’re not being malicious. They’re a business and they’d do poorly if it turned out they were malicious and using this information for spying or anything of that nature. 

If you’re running from an oppressive government, I’d probably not use them. They’re a business and that means they’re likely to respond to lawful requests – and laws around the globe can be pretty terrible.

In fact, if you’re doing anything that’s even remotely secure, I’d suggest not doing so over TeamViewer. Sure, when the application is terminated you can verify that it’s down, but at the same time don’t connect to your remote device to do your banking. That’d just be silly regardless.

As I stated above, I’m quite okay with the potential privacy and security implications. I don’t use Linux because of any philosophical reasons, I use Linux because it just works. If you’re different and object in some way, you should probably just move on and use alternative software to remotely manage your devices.

Closure:

And there you have it! It’s yet another article in the books, another article in the records. Traffic has been high lately, and that’s great. Things are growing in a linear feature and I’m okay with that. Even my Reddit sub is growing – at 50 viewers, up from just a few when I first took the sub over. So, things are going great.

Thanks for reading! If you want to help, or if the site has helped you, you can donate, register to help, write an article, or buy inexpensive hosting to start your own site. If you scroll down, you can sign up for the newsletter, vote for the article, and comment.

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