A distributed denial-of-service attack aimed at AT&T's DNS (Domain Name System) servers has disrupted data traffic for some of the company's customers.
The multi-hour attack began Wednesday morning West Coast time and at the time of this writing, eight hours later, does not appear to have been mitigated.
"Due to a distributed denial of service attack attempting to flood our Domain Name System servers in two locations, some AT&T business customers are experiencing intermittent disruptions in service," an AT&T spokesman told IDG News Service by email. "Restoration efforts are underway and we apologize for any inconvenience to our customers."
The attack appears to have affected enterprise customers using AT&T's managed services DNS product.
"Our highest level of technical support personnel have been engaged and are working to mitigate the issue," AT&T said in a message on a service status page.
But it added there is "no estimated time" for restoring the service.
DNS is responsible for converting human-friendly domain names into the numeric IP (Internet protocol) addresses that computers use to route data. When it fails, computers are unable to route data to its intended destination, even though the destination server remains online and accessible.
A distributed denial-of-service (DDoS) attack attempts to flood a server or system with so many packets of data that it becomes difficult or impossible to reach for legitimate traffic. It doesn't necessarily stop the server from working, but the overload of data results in the system being all but unusable.
Service is returned to normal when the attack stops or when engineers find a way to absorb or deflect the nuisance traffic.
"We got our first report of problems at 6:31 a.m. Pacific time," said Daniel Blackmon, director of software development, at Worldwide Environmental Products. The company tests vehicle emissions and has remote units deployed that report back to central servers.
"The problems mean none of the equipment we have in the field can contact our servers, and there is a limit to the amount of information they can hold offline."
Martyn Williams covers mobile telecoms, Silicon Valley and general technology breaking news for The IDG News Service. Follow Martyn on Twitter at @martyn_williams. Martyn's e-mail address is email@example.com