Microsoft sites, including search engine Bing and MSN.com, were knocked briefly offline Friday after bad code was rolled out, according to a report.
Speculation began on Twitter that the sites were brought down by cyber-attackers in the wake of high-profile attacks against U.S. targets, including the attack on Sony Pictures in November.
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But, a source speaking to Reuters said the outage was not caused by an outside attack -- rather, glitchy update code.
The source said the company struggled to immediately roll-back the code, which would have potentially cut the outage time down considerably. After the roll-back failed, engineers were forced to shut down its groups of linked servers to get back to a safe point where the sites were fully operational.
Bing, which powers Yahoo Search, was down for about 20 minutes.
Microsoft said in a statement Friday that its sites suffered a "brief, isolated services outage," but did not elaborate further.
The company could not be reached for comment Saturday.