![]() You must remember to append the new non-standard port number to your SSH connection attempts from this point on. I suspect many folks use 2222 as the replacement port number, so you may want to standardize on something a little more unique. You can comment out the default port setting and add another line, as I've done below: #Run SSH on a non-standard port There's already an entry in the sshd_config file. No more port 22Īnother common change is to configure SSH to listen on a different port than the standard 22/tcp that we've all memorized. Note: You can limit connections via iptables, too. You can discover more information on the man page for sshd_config.Ĭhallenge - be careful about exactly who is authorized. I wrote them in that order on purpose-that's the order in which they are processed. I'd put it near the PermitRootLogin no setting.īy the way, you can actually filter with all of the following settings: AllowUsers, DenyUsers, AllowGroups, DenyGroups. In the SSH configuration file, add the following line (it's not in there by default): AllowUsers user1 If you're already preventing the use of the root user account across SSH, why not go a step further and explicitly state which users can connect to the server? Perhaps you have a regular non-root admin account you use or one that's already configured with sudo privileges. PermitRootLogin noĬhallenge - your organization has embraced sudo, right? 5. Open the SSH configuration file, and then uncomment the PermitRootLogin line. Once you've established your SSH connection using a standard user account, use su or sudo to elevate your privileges. Send standard user credentials across the network instead of root credentials. Prevent the root user from crossing the network via SSH Uncomment it, and replace the yes value with no. Open the /etc/ssh/sshd_config file in Vim, and then find the line that reads PermitEmptyPasswords. You may have other utilities, such as Pluggable Authentication Modules (PAM), regulating your regular passwords, but it's also a good idea to make sure SSH enforces responsible security settings, too. This seems like a no-brainer, but empty passwords are clearly a bad idea. Any time you make a change to the configuration file, you must restart the service.Ĭhallenge - Is the banner message consistent across all the SSH devices on your network? 3. Note: I'm not going to remind you to restart SSH from this point forward. Save your changes in Vim with :wq and then restart the SSH service: # systemctl restart sshd You do remember that you can use the forward-slash character in Vim's Command mode to keyword-search a file, right? For example, /banner # vim /etc/ssh/sshd_configįind the line that reads # no default banner path, and then uncomment the next line (it says Banner). Open the sshd_config file in Vim, and find the line that reads Banner. Next, tell SSH to use the banner message. Remove any information that's already in the file. ![]() Obviously, you'll want to come up with something specific to your organization. # vim /etc/ Warning! Authorized use only. Then we'll open the sshd_config file and tell it to use the content of as the banner. First, we'll write the banner message in the /etc/ file by using Vim. You can actually provide some pretty good information in banner messages, too. Set a banner messageĪdmittedly, this is as much about legal requirements as anything else, but again, this setting only takes a moment. And who hasn't made a mistake in Vim? # cp /etc/ssh/sshd_config ~/sshd_config_originalĬhallenge - Do you consistently back up configuration files before making major edits? 2. It's easy, takes only a moment, and protects you in case of a mistake when editing the file. This is a common bit of advice, but it's a real one. ![]() How well do you know Linux? Take a quiz and get a badgeįirst, back up the configuration file before making major changes.Linux system administration skills assessment. ![]() A guide to installing applications on Linux.Download RHEL 9 at no charge through the Red Hat Developer program. ![]()
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