What is a Jump Server? - Configuration Guide

As network perimeters expand and cybersecurity challenges grow, implementing jump servers has become a vital strategy for enhancing security in IT infrastructures. These specialized servers manage controlled access to network resources, acting as a secure gateway that shields sensitive internal systems from potential threats.

By mitigating the risks associated with direct remote access, jump servers serve as a critical checkpoint, ensuring that only authenticated users can reach essential assets.  

What Is a Jump Server?

A jump server (jump host or bastion host) is a dedicated intermediary server designed to manage and control access to a network's different zones or segments. It’s typically placed between a user's device and the target hosts, restricting direct network access to protect sensitive systems.

This setup is particularly useful in environments that manage highly sensitive data, where minimizing potential exposure to threats is critical.

Everyday use cases include managing remote servers through SSH, providing a controlled path for database access, and enabling secure admin tasks in demilitarized zones (DMZs) without exposing the broader network.

Benefits of a Jump Server

Jump servers provide a range of benefits that are particularly valuable in securing IT environments and simplifying network management. Here are some of the key advantages:

• Enhanced Security: Jump servers ensure all traffic to internal networks goes through a monitored and controlled single access point. That limits the attack surface by preventing direct access to the network from less secure external networks​.
• Centralized Access Control: By funneling all remote access through a jump server, organizations can more effectively manage and monitor who accesses their network and what they access. This centralized approach simplifies the enforcement of access policies and improves compliance with security protocols​.
• Audit and Monitoring: With all traffic passing through a single point, jump servers facilitate detailed logging of access and activities. This data is crucial for audit trails, which can help in detecting, investigating, and responding to potential security incidents​.
• Reduced Complexity: They can lower the complexity of network configurations by minimizing the number of direct connections allowed across the network. That simplification can reduce overhead in managing network security settings and user permissions​.

Downsides of Using a Jump Server

A jump server, while a powerful tool, can also be a potential risk in a network's design. In 2015, a compromised jump server allowed attackers access to over 21.5 million records in one of the largest breaches of government data in the history of the United States. There are several ways of improving the security of the jump server, including:

• Properly Subnetting/Segmenting the Network: Secure VLANs using a firewall or router to ensure isolation of sensitive areas.
• Higher Security Authentication: Use multi-factor authentication to add an extra layer of security.
• Regular Updates: Keep the operating system and software on the jump server up to date to protect against vulnerabilities.
• Access Control Lists (ACLs): Use ACLs to restrict access to the jump server to only necessary users and services.
• Restricted Internet Access: Do not allow outbound access to the rest of the internet from the jump server.
• Program Restrictions: Restrict which programs can be run on the jump server to limit potential misuse.
• Strong Logging: Enable detailed logging for monitoring and alerting of suspicious activity.

Given the high level of risk a jump server can represent, VPNs are an excellent choice to secure access to your jump server. At Netmaker, we've designed a remote access platform that is perfect for securing access to your servers. We use WireGuard, which has modern cryptography and secure, mutual key authentication. This minimizes many of the above threats, and helps keep your jump server out of the hands of untrusted parties.

Jump Server Core Components and Setup

Setting up a jump server involves several core components and steps to ensure it functions as a secure access point within your network architecture. Here’s a breakdown of what you need to do:

1. Select Hardware or Virtual Environment: Depending on your network setup and resource requirements, decide whether to use a physical server or a virtual machine​.
2. Install the Operating System: Choose an operating system that supports robust SSH operations, such as Linux or Windows Server. Install the OS on your selected hardware or virtual environment.
3. Assign a Static IP Address: Configure a static IP address for the jump server to avoid issues with DNS resolution and IP changes that could disrupt connectivity​.
4. Install and Configure SSH Server: If using Linux, install the OpenSSH server using your package manager. For Windows, you might install and configure the Windows SSH Server included in recent versions of Windows Server​.
5. Harden SSH Configuration: To reduce the risk of automated attacks, change the default SSH port from 22 to a less commonly used port. Disable password authentication and enable key-based authentication. Configure the SSH server to disallow root logins​.
6. Set Up Firewall and Security Measures: Configure the firewall to allow SSH traffic only from specific IP addresses or ranges. Implement two-factor authentication and use tools like fail2ban to monitor and block suspicious login attempts.
7. Configure User Access: Create necessary user accounts and assign them the minimal required permissions for their role. For each user, setup and configure authorized keys for SSH access.
8. Test the Configuration: Using SSH to access the jump server from a client machine, ensure all configurations work as expected. Also, validate that all security measures, such as key authentication and port changes, function correctly​.

Steps 5-7 can be modified to expose SSH access only over a VPN endpoint. If you choose this method, you can also set up user access within the VPN itself.

Now, your jump server is ready to go. Let’s explore some more advanced configurations.

Jump Server Advanced Configurations

Here are some extra options for making your jump server more secure:

• SSH Key Management: Implement key-based authentication instead of passwords to reduce the risk of brute-force attacks. Manage and rotate SSH keys regularly to maintain security integrity​.
• SSH Agent Forwarding: Use SSH agent forwarding cautiously. It allows a remote server to use your local SSH keys for the duration of your session. While it enhances usability by not requiring SSH keys on the jump server, it should be used with single-purpose keys to limit potential exposure​.
• ProxyJump and ProxyCommand: Use ProxyJump to simplify secure connections through one or more intermediate hosts. It's easier and more secure than ProxyCommand because it encapsulates all forwarding in a single command and maintains encryption throughout the transit path.

Here’s an example of what your config file will look like:

# In your ~/.ssh/config file

Host finaldestination
HostName final.destination.server
User username
ProxyJump jumpserver1,jumpserver2

This directs your SSH client to first connect to jumpserver1, then jumpserver2, and finally to the final.destination.server using the username provided. It simplifies the connection process to multi-hop environments and keeps the traffic encrypted across jumps.

Jump Server FAQs

Q: How do jump servers enhance security?

A: Jump servers minimize the risk of exposure and attack by isolating critical network areas and requiring all user activities to pass through this controlled path. This allows for better monitoring, activity logging, and adherence to strict access controls, making it harder for unauthorized users to access sensitive areas of a network​.

Q: Are jump servers the same as VPNs?

A: No, jump servers and VPNs serve different purposes. A VPN extends a private network across a public network, allowing users to send and receive data as if their devices were directly connected to the private network. In contrast, a jump server acts as a single access point that users must first connect to before accessing other parts of the network, providing a layer of security and control not focused on by typical VPNs​.

Q: What are some best practices for managing jump servers?

A: Best practices for jump servers include implementing multi-factor authentication, enforcing strict access controls, keeping the operating system and applications updated with security patches, and using network segmentation to isolate the jump server from other parts of the network. Regularly monitoring and auditing the jump server is also crucial for detecting potential security issues​. Restricting access behind a VPN (like Netmaker) helps accomplish many of these goals while adding an extral layer of security.

Final Thoughts

Jump server deployment can significantly fortify an organization's defenses against unauthorized access if setup properly.

And if you want to learn more about securing access to your jump server, Netmaker is here to help.

Using the WireGuard protocol, we simplify the creation and management of virtual networks, enabling fast, secure, and distributed networking across various environments.

Ready to streamline your network management and secure your digital environments effectively? Contact us today to learn more.