Technological advancements and the widespread nature of the Internet have allowed many businesses to evolve and rediscover themselves. As a part of these ongoing changes, many corporations and businesses have started using the cloud for better efficiency. However, security is of paramount importance when it comes to remote working. That is why VPNs are necessary. Different types of VPNs can be used to protect online data. One such VPN is the SSL VPN. It is a combination of the SSL encryption protocol and the functionality of a VPN.
What is SSL VPN?
SSL VPN stands for Secure Sockets Layer Virtual Private Network, which allows users access to private and virtual networks without any specific client software. Those familiar with a VPN should know that traditionally, every VPN provider also offers a VPN client that is necessary for the user to connect to the VPN server or network.
This is why, the absence of this client software is what makes SSL VPN so versatile. Since there are no entry barriers, people can use an SSL VPN on any device simply from the web browser and enjoy an encrypted connection.
As the name suggests, the VPN explicitly uses SSL or TLS (Transfer Layer Security) protocols for VPN tunneling. However, it is not decided by an individual connected to the network but is set automatically by the VPN based on the newest and most updated cryptographic protocol that can be found on the user’s browser.
Similarly, the individual does not have to worry about any updates. By only updating the web browser or the OS, users can ensure the VPN is using the latest protocols available.
SSL VPNs are mostly used in organizations or enterprises to enable remote working in a safe and protected environment. Users can connect to the intranet of a company to securely access its resources. It also expands this sphere of security to those connecting from outside a company using the public internet.
The following article explores the various facets of an SSL VPN in great detail. Furthermore, the OpenVPN community also offers an explanation regarding SSL VPN, its architecture, and its cost on the official platform.
How does SSL VPN work?
Now, let us figure out the intricacies behind the workings of an SSL VPN. As we have earlier established, the VPN relies on TLS and SSL, (in fact, modern SSL VPNs primarily use TLS instead of the outdated SSL) protocols to establish a secure and remote connection to the network. It allows authenticated users to establish a secure connection to internal HTTP and HTTPS services using only a standard web browser. The entire process can be broken down into several steps:
- Initial Handshake – During this phase, the user relies on the web browser to reach out to the SSL VPN gateway for the initial handshake.
- Network Authentication – The gateway has a certificate issued by the server that it uses to authenticate the user information exchanged during the handshake.
- Encryption Negotiation – After the gateway authenticates the identity of the user, the browser and the VPN server negotiate the encryption algorithm that will be used for the following data exchange.
- Key Exchange – Finally, both exchange a shared secret or a set of public keys to establish the tunneling process.
Here’s the entire process in detail:
Step 1. A Connection is initiated
First, the user has to launch the web browser to access the VPN portal provided by the VPN service. Here, it enters his details, i.e., his credentials, and then the browser sends the data to the VPN server in question. Hence, a connection is initiated. If the next step fails, it will return an error on the portal.
Step 2. Initial Handshake and Authentication
The web browser then reaches out to the VPN gateway for the initial handshake. During this process, it passes on the information provided by the user for the gateway to authenticate with the VPN server. This process is necessary to weed out infiltrators. Once authenticated, the servers allow the browser to connect.
Step 3. Establishing a Secure Connection
Now, the browser and server negotiate to create a secure channel for the transit of data and resource exchange. This step is composed of two parts:
A. SSL HANDSHAKE
The server and browser then exchange information about the encryption profiles available and which one to use. Thus, they exchange the corresponding cryptographic keys, verify security certificates, and agree to the encryption parameters and the session keys.
B. TRAFFIC ENCRYPTION
After the SSL handshake, any data exchanged between the browser and server undergoes encryption. Hence, a secure connection is established, which will effectively prevent anyone outside the network from prying into the traffic, preserving the integrity of the data, even if it uses the public internet for transmission.
Step 4. Data Transmission
Then comes the data transmission, where the browser can safely send and receive information from the server. It uses a secure and encrypted connection, which protects the data from outsiders, and any unauthorized person can’t gain access to this channel.
While these are the common steps involved, the actual process might differ for any number of SSL VPNs due to the difference in the user interface and how the VPN is implemented. Thus, we urge the readers to take note of this.
Types of SSL VPN
This brings us to the next topic: the types of SSL VPNs. A company can implement SSL VPNs in any manner. Depending on how the VPN is implemented, the user is restricted in how and what resources it can access. In principle, SSL VPNs can be implemented in two different ways: SSL Portal VPN and SSL Tunnel VPN.
SSL Portal VPN
SSL Portal is a simple implementation of the SSL VPN. It is also called a clientless VPN or web-based VPN. SSL Portal offers remote access to a network using only a standard web browser. It is also the most popular type of SSL VPN and is widely used, allowing connected users to access the intranet of an organization to access the applications, files, and other resources available.
The VPN works like any other HTTPS-secured website, where the VPN gateway first authenticates the user before allowing him to access resources on the server. And for this, it uses a web portal. The administrator can further create privilege rules that restrict the user from accessing other resources outside his purview.
All this is good, but SSL Portal VPNs come with a few limitations. The major issue with this type of VPN is that it only allows a single connection at a time. Another caveat is that it works only for those resources that are browser-friendly. Thus, running legacy apps or network services requires additional support.
SSL Tunnel VPN
Then we have the SSL Tunnel VPN. It is also known as SSL Network Extender, or SNX. In principle, the VPN also creates a secure and encrypted tunnel between the user’s device and the private network he is trying to connect to. However, it is much smoother than SSL Portal as the user is able to access the network resources directly. However, it does require VPN client software to be installed on the user’s device.
Companies can use the SSL Tunnel VPN to extend the connected user’s access to more resources. When the user establishes a connection with the VPN gateway, it prompts the user to download an SSL Tunnel VPN app, which can deliver active content using popular technologies such as JavaScript or Flash. Hence, users can access even those resources that are not supported by the browser.
Key Differences Between SSL Portal and SSL Tunnel VPN
Although both SSL VPNs are the same in practice, how they are implemented is completely different. This difference further extends to user convenience and network accessibility. While an SSL Portal is more convenient for the user, it is much more restrictive. Moreover, there is an additional risk of human error. SSL Tunnel on the other hand, does require client software, making it less convenient, but the app allows the user to access the entire network.
Benefits of SSL VPN
SSL VPN is useful, no doubt, but what are the actual advantages of using this VPN? Find the several benefits of SSL VPN below:
- It uses the latest TLS technology, which renders the use of client software moot.
- SSL VPNs are easy to deploy.
- It offers relatively more sophisticated encryption and data security than traditional VPNs.
- It requires less administrative overhead and tech support.
- SSL VPNs can run on any web browser, no matter the OS; hence, the entry barrier is very low.
- It is very easy to use, and there is no need for a complex installation process.
- While VPN protocols like L2TP and IPSec operate at Layer 2 and Layer 3 of the OSI networking model, respectively, they require additional support and configuration, whereas SSL operates at the Transport Layer, which allows the network traffic to undergo securely tunneled circuits much more easily.
- And finally, SSL VPNs can be further configured to enable precise control and yield greater efficiency, as they can be used to create specific tunnels to applications instead of branching to the whole network.
Security Risks associated with SSL VPN
When looking at SSL VPNs, we should also factor in the various limitations and security risks associated with the technology. Below are a few disadvantages of the SSL VPN:
- The VPN can be susceptible to malware infestations such as spyware, worms, and viruses like the Trojan Horse.
- A remote user without proper protection can inadvertently spread viruses and malware across the entire network.
- The split tunneling feature on an SSL VPN can be exploited by hackers and malicious entities. They can rely on the unsecure channel as an intermediary to launch an attack.
- Human error also plays a huge part in an SSL VPN’s security concerns. If the user leaves a session open and moves away from the terminal, anyone can use the same device to access the network without any issues.
SSL VPN vs. IPSec VPN
SSL VPNs have recently become more popular, but there is another VPN that is used by businesses on a large scale, and that is the IPSec VPN. Due to this, we have to compare the two to figure out which is a better fit for the user.
| Factor | SSL VPN | IPSec VPN |
| Software | SSL VPNs rely on web browsers and do not require any specific software. | IPSec VPNs, on the other hand, need client-based software to establish a connection. |
| Network Security | SSL VPNs only secure browser traffic and are prone to cyber-attacks. | IPSec VPNs secure any traffic going out from the device and can prevent attacks such as MITM. |
| Data Encryption | Encryption is applied only to the data sent or received by the web browser. | Encryption is applied to every data transmitted by the device. |
| Setup and Configuration | SSL VPNs are easier to use, and there is next to no configuration. | Setting up and configuring an IPsec VPN requires technical knowledge. |
| Protocol | They use the SSL or the TLS protocol. | They use the IPSec protocol. |
| Authentication | They use third-party certificates and public keys for authentication. | They rely on private keys that are shared only between the client and the server. |
| Network Access | Offers much more refined access where the user can access a specific app, service, or resource. | Connects the user to the entire network. |
Conclusion
SSL VPN is beneficial to corporations and businesses for information security. Since many businesses have migrated to the cloud for their operations and actively rely on remote working, it is paramount that data remain safe in transit. And SSL VPN is the solution to their worries. However, even SSL VPN is not without its faults. If the company wants it to work on resources that are not browser-friendly, then it has to add overhead, which increases the cost and complexity of the entire operation. Then there are online threats that can render an SSL VPN vulnerable, such as MITM attacks, and phishing.
All in all, the SSL VPN is here to stay if current growth is any indication. The VPN is a comprehensive cloud business solution that is likely to grow. And if a recent study done by Industry Research is to be believed, then the current SSL VPN market of $1600 million is only going to grow further at a rate of 4.59%, with expectations to reach $2094.77 million by 2028.