A widespread internet outage caused several major websites to shut down Thursday afternoon,Slabu including Amazon, Delta, Capital One and Costco.

Akamai, a content distribution network that helps with the spread of data around the internet, posted on Twitter that a software configuration update caused a bug in its DNS system.

A DNS, or domain name service, helps match a website's name to its IP address. If the DNS fails, it becomes impossible to search and connect to a website by name.

The outage lasted approximately one hour. Akamai says it rolled back the software configuration update. By around 1:13 p.m. ET, the site read "all systems operational."

When reached by NPR, Akamai said, "We have implemented a fix for this issue, and based on current observations, the service is resuming normal operations."

Akamai also confirmed that the outage was not due to a cyber attack.

A similar widespread outage occurred in June when another content delivery network, Fastly, experienced a software bug. Websites like CNN, The New York Times, Twitch and Reddit were down for nearly an hour.

The outages, while temporary, are raising concerns about the number of websites that rely on just a few content delivery networks like Fastly and Akamai, creating a more fragile internet ecosystem.