SSTP stands for Secure Socket Tunneling Protocol, and it’s a vital component of many online security tools. Due to its use of secure encryption, many people see SSTP as a form of Virtual Private Network – a tool which allows web users to surf anonymously and hide their identity and location.

As the name suggests, an SSTP client acts like a “socket”, connecting two computers or other digital devices together. Secure Socket Tunneling Protocol systems also employ a technique called “tunneling” to create that connection. As we’ll see, both of these terms have important implications when understanding the strengths and weaknesses of SSTP based networking solutions.

Introducing SSTP

SSTP isn’t a new technology by any means. It’s essentially an updated form of the Point to Point Tunneling Protocol, which was developed by Microsoft in the 1980s. In fact, SSTP first appeared in Windows Server 2008 as a direct update of PPTP.

The intention of SSTP was simple: to allow remote users to connect securely to servers located elsewhere in the world. With businesses operating in a more “networked” fashion, and workers often distributed across wide geographical areas, it’s easy to see how this kind of connection has huge benefits in all sorts of scenarios.

How does SSTP work? In a similar way to PPTP, SSTP wraps up packets of data in a protective sheath. When using Secure Socket Tunneling Protocol, users are required to connect via a standard Transmission Control Port (TCP), which allows the target server to initiate authentication procedures.

This involves sending a couple of encryption keys to the user’s system, which form the basis for the SSTP tunnel. When that’s done, the packets can be sent with relatively high levels of security directly to the server.

The way the secure socket tunneling protocol works has made it the ideal ally for VPN providers. They can supply the VPN client and a network of servers, while SSTP applies a suitable level of encryption, allowing users to transmit and receive data securely.

However, as we’ll see, not all VPNs use this method, and there may be some good reasons to avoid SSTP client VPNs.

What port does SSTP use?

Before looking at VPNs in more detail, it might be handy to run through some more technical aspects of the secure socket tunneling protocol. The most important thing here is probably the TCP port that SSTP uses. In all cases, the protocol will communicate via TCP port 443.

You might have seen this number referred to when accessing “HTTPS” websites. That’s no accident, because HTTPS websites are secured by SSL, which is closely related to SSTP. The security provided by this encryption makes HTTPS website much less vulnerable to phishing attacks. VPN connections work with exactly the same port.

In terms of encryption, an SSTP client will always use 2048 bit encryption techniques. This employs what is known as “asymmetric cryptography”, and is the preferred security solution for online security firms like Digicert.

It’s also worth noting that while the secure socket tunneling protocol was developed by Microsoft, it has been adapted for use across other major operating systems, including Linux builds.

However, Microsoft haven’t ported SSTP directly for Mac or iOS, although SSTP client tools are available for MacOS (iSSTP is the one to try). So whatever device you use, an SSTP client should be available.

What is an SSTP VPN and how do they work?

An SSTP VPN is a virtual private network which has been setup to use the secure socket tunneling protocol as its major form of encryption and data transfer.

One key thing to note about Secure Socket Tunneling Protocol is that it uses SSL encryption instead of IPSec. This is an important dividing line in the world of VPNs, and it’s useful to know how these two protocols differ.

Both provide sophisticated encryption. But IPSec has known issues with negotiating firewalls, network address translation errors. IPSec based VPNs also have to be installed on each machine, while SSL/SSTP is integrated into Windows.

However, there’s another key difference. SSL/SSTP VPNs almost always run through web browsers, which is how Microsoft intended them to be used. IPSec often works via separate clients, providing better protection for apps like torrenting clients and online games.

This is actually both a weakness and a strength of Secure Socket Tunneling Protocol. On one hand, it might not be ideal for gamers or torrenters. But on the other, it offers a built-in, affordable VPN service for businesses and people who need browser protection, while it also works around NAT firewalls extremely effectively.

Moreover, if you use an Secure Socket Tunneling Protocol client, you might be able to get the best of both worlds. These tools are available for Macs, smartphones, Linux and Windows. They provide all-round protection for all online apps, and allow users of non-Windows systems to access Microsoft’s protocol – a neat workaround.

The bottom line is that the secure socket tunneling protocol is an increasingly popular alternative to IPSec based VPNs. It has its limitations, but delivers strong encryption and is well adapted for business users. But are there any security concerns for VPN users to worry about?

Is SSTP secure?

One major issue for many VPN users is that the secure socket tunneling protocol was developed by Microsoft and remains a proprietary technology of the Seattle-based tech giant. This means that, theoretically Microsoft could add back doors or other vulnerabilities, rendering the protocol much less effective, and we don’t have any way of knowing whether this has been done.

In general, though, Secure Socket Tunneling Protocol is reckoned to be one of the most secure VPN protocols around. It offers an extremely reliable way to breach firewalls and unlock streaming sites, while its SSL-based encryption is almost impossible to distinguish from regular web traffic.

It’s not offered by all VPN providers, but these strengths mean that many users can benefit from sourcing an Secure Socket Tunneling Protocol client. They may not be for everyone, but if you trust Microsoft, they could be ideal.