Akamai is confirming that network outages this morning were caused by a distributed denial of service (DDoS) attack that affected its DNS management system.

The performance problems affected Microsoft, Google, Yahoo and antivirus update services from Symantec and TrendMicro, which are among Akamai’s 1,100 customers. Some of the largest affected sites were able to switch their DNS settings to their internal network, rather than akadns.net, which handles domain name service management for Akamai customers. The akadns.net system routs requests for high-volume customer web pages to content stored on its network of distributed servers, easing traffic to the client’s main server and speeding delivery to the end user. Akamai performs similar function for downloads of audio and video files, software patches and antivirus definitions.

The outages mark the second disruption of Akamai’s network in less than a month, following a similar incident May 24.