The world's best software developers have a not-so-well-kept secret: Most of the crucial back-end systems that power the world rest on a precarious foundation of software held together with the digital equivalent of popsicle sticks and chewing gum. But they're also excited about an emerging programming language that promises something better.

For the fourth consecutive year, Rust topped Stack Overflow's 2020 survey of the "most loved" programming languages in software development, and there are some easy-to-understand reasons why. Rust was designed to prevent developers from making memory-handling mistakes that can lead to damaging (and prevalent) security flaws, and it also helps those developers figure out why their software isn't working.

Sign up for Protocol newsletters

That's why the language is increasingly gaining momentum, as a new generation of companies start to rewrite their critical infrastructure for the cloud computing era. AWS used Rust to build Firecracker, an open-source serverless computing platform that runs the company's strategically important Lambda and Fargate services. Dropbox rewrote some of its core systems software in Rust as part of the process of rolling out its own hardware infrastructure. And at Mozilla, where Rust was originally developed, the language was used to build the core browsing engine at the heart of Firefox.

Those companies are all hoping to avoid the security mistakes of the past. Rust may have its own issues — it's particularly difficult to learn, for instance — but it's "the industry's best chance for addressing this issue head-on," said Ryan Levick, principal cloud developer advocate at Microsoft, in a recent talk.

Lessons from the past

Over the last few decades, a huge percentage of the low-level systems software that controls the world's computers has been written in a language called C++, which was first released in 1985 and became a big part of Microsoft's product strategy. C++ is a powerful and efficient language that introduced the object-oriented programming concepts, now present in so many languages, to the seminal C language. But it has one glaring drawback.

It is very, very easy for programmers using C++ to make memory-handling mistakes. And according to Levick, over the last 15 years or so, around 70% of the security vulnerabilities in Microsoft products that required a CVE disclosure were memory-related.

Those mistakes allow malicious attackers to flood memory registers with data, creating a "buffer overflow" security problem that can overwrite data in memory registers adjacent to one program, and allow attackers to run code without the user's knowledge or consent. "C++, at its core, is not a safe language," Levick said in his talk.

By design, Rust prevents developers from making those mistakes.

"For years and years, Microsoft has been trying to get its C++ developers to use best practices and write more secure code," said Nell Shamrell-Harrington, senior staff research engineer at Mozilla and one of the people working directly on the advancement of the language. "In Rust, that security is built into the code itself."

Rust also helps developers debug their code by providing hints and pointers when their software isn't working, rather than just throwing out a vague error message, Shamrell-Harrington said. In some cases it will pinpoint the exact line of code that needs fixing, she said, saving developers a ton of time and anxiety.

The downside? Rust has a steep learning curve. "I would not recommend anybody use it as their first language, and maybe their second," Shamrell-Harrington said. Newcomers to Rust find it fairly easy to learn the basics, she said, but struggle when trying to move into the intermediate stage.

The numbers bear that out: Only 3.2% of developers surveyed by Stack Overflow actually use Rust on a regular basis. Twice as many people are still using Assembly, a low-level machine language that dates back to the 1940s. In fact, one of Shamrell-Harrington's jobs is to help produce content for the developer community that will bridge the knowledge gap and make it a more widely used language.

The one of many?

Rust is by no means the only modern programming language that provides memory safety for its users. Longtime stalwart Java offers some memory-handling protections. And Swift, Apple's iOS-friendly application development language, also puts strict boundaries around memory handling.

But they're high-level languages, which trade efficiency to gain ease of use. In comparison, Rust was designed for writing the sorts of lower-level systems software that runs the internet, offering performance at the same level provided by C++ and well beyond the capabilities of languages such as Java and Swift.

Perhaps Rust's main rival is Go, developed at Google, which is also used for system-level development and emphasizes memory safety. It's currently used more widely than Rust and is also considered easier to learn — but has less cachet among developers according to Stack Overflow's survey and lacks some of Rust's features.

As more and more business activity flows through software delivered over the internet, secure software has never been more important. If the best way to prevent 70% of serious security vulnerabilities is to adopt a programming language that makes it impossible to introduce memory-related security flaws, expect to see a lot more Rust in the future.