NetScout issued a press release claiming the outage was a BGP leak, but after experts (including, apparently, the NetScout employee quoted in the press release) said that wasn't the case, NetScout walked back the certainty of its claims.
What they're saying:
"Absent more forensic evidence, we can't speculate about the cause of that specific outage," NetScout said via email.
"Yesterday, as a result of a server configuration change, many people had trouble accessing our apps and services. We've now resolved the issues and our systems are recovering," Facebook said via Twitter on Thursday.