The site confirmed that AT&T, Verizon, Charter Spectrum, Comcast, Sprint, Time Warner Cable, US Cellular, and Vonage were among those affected.
Calling issues have been resolved by the provider, Level3 & is back to normal. Thanks for your patience. https://t.co/DIMKEldejM— John Legere (@JohnLegere) October 4, 2016
Level 3 acknowledged the issues, tweeting: "We're aware of a situation impacting voice svcs. Our team is working to ID cause. We will provide updates as more info is available."
We're aware of a situation impacting voice svcs. Our team is working to ID cause. We will provide updates as more info is available.— Level 3 Network Ops (@Level3NOC) October 4, 2016
Today our voice network experienced svc disruptions affecting some NA customers. We restored svcs by 9:31MT. We're investigating root cause.— Level 3 Network Ops (@Level3NOC) October 4, 2016
One sysadmin on the NANOG list did speculate that the outage might be due to a denial of service attack, writing "This could be DoS attack."
In response well-known security expert Valdis Kletnieks had this to say: "Or a missing comma in a code update. Or a fumble-fingered NOC monkey. Or.... You have any reason to suspect a DoS attack rather than all the other possibilities?"
Source code for software used to carry out distrubuted denial of service attacks was leaked recently, as iTWire reported.
And security technologist Bruce Schneier had recently pointed out that he had been told by people in the industry that there had been probes to test the defences of the Internet.