Insecure APIs a Growing Risk for Organizations

Application programming interfaces (API) that connect enterprise applications and data to the Internet are subject to the same vulnerabilities as regular web applications and need to be addressed with at least the same rigor.

In fact, the direct external access to transaction updates and mass data that APIs enable subject them to additional threats that web applications rarely encounter, according to Forrester Research.

In a report summarizing some of the major security issues surrounding API use, the analyst firm warned about API breaches becoming increasingly common and the next big attack vector for threat actors.

"As organizations are securing their web applications, they can't forget about their APIs," says Forrester analyst Sandy Carielli. "Security pros must specifically build in API security and not assume that it's rolled into their existing web application protections."

An API basically allows applications or components of applications to communicate with each other over the Internet or a private network. Initially, most organizations used them within a secure private network or accessed them through secure communications channels. But, increasingly, organizations have begun using APIs to open up access to internal applications and data to partners, suppliers, customers, and others. Many see APIs as fundamental to enabling digital transformation initiatives and powering a new generation of mobile applications.

A survey of 1,500 developers, architects, QA professionals, and others conducted earlier this year by SmartBear found 77% of organizations represented in the survey both develop and consume APIs. The most common use case for APIs continues to be interoperation between internal tools, teams, and systems and reducing development time and cost. Other popular use cases include partnering with external organization, extending product or service functionality, and absorbing data and features from external products.

According to Forrester, many of the security issues surrounding APIs have been years in the making and have to do with the shift away from early SOAP messaging protocol-based APIs to today's REST APIs.

Previously, SOAP APIs were typically accessed securely over VPNs or two-way encrypted connections. REST APIs, on the other hand, are designed for access through browsers and mobile apps. When a mobile user makes an airline reservation on his phone, for instance, a REST API conveys the user's instructions to the airline or travel services vendor's back-end applications and delivers the response back to the user.

REST APIs are open for exploitation through commonly available client-side inspection and hacking tools, just like web applications are unless protected. Long-held security best practices such as least-privilege data access and server-side data validation are therefore as critical to APIs as they are to web applications, Forrester says.

The tools for exploiting APIs are not complicated, Carielli says.

"Basic proxies that attackers use to manipulate HTTP and HTTPS requests would apply here, too," she says. "Sometimes it's as simple as changing a parameter in the HTTP request."

Rogue Endpoints
Additionally, REST APIs can provide direct access to transaction updates and other important data on back-end systems. That's because firms can often fail to track all API endpoints buried deep within their mobile apps or web apps or put adequate controls in place to authenticate and verify API calls. Such rogue endpoints can put them at heightened risk of unauthorized access and data exposure, Forrester says.

Carielli says if a publicly accessible API doesn't go through the organization's API authentication and authorization gateway or through a web application firewall that might validate the request format, then an external party might have access to any data to which the API has access.

"Remember that APIs serve to make various application data and functionality available to developers outside of the organization," Carielli says. "Because API endpoints can be accessible to anyone externally that calls the API, a rogue endpoint that returns sensitive information is high risk."  

One common result of unauthenticated API endpoints is that customer data gets exposed. For example, if an API to access customer transaction data is accidentally deployed without putting in the proper authentication and authorization checks, anyone who used the API could see a lot of sensitive customer information, Carielli says.

The sheer diversity of technologies, designs, and contexts in which APIs are used makes securing them a challenge, Forrester said in its report. The analyst firm outlined several measures that organizations can take to bolster API security.

For instance, in developing APIs, organizations need to pay attention in the design stage to security measures like default deny and verification of any client-supplied data. Organizations should ensure that all API traffic, just like web application traffic, is encrypted but in a manner so as not to impact performance. Also critical is the need to authenticate API calls at every layer and to stop thinking of APIs merely as an interface layer between applications, Forrester said.

"Whether the API ultimately touches data, legacy, or modern application architectures, or even hardware or firmware, work through those touch points collaboratively with the security owners of the relevant systems," the analyst firm advised.