Both NASDAQ and BATS were recently targeted by cyber attacks.

"The two US stock exchange operators have fallen victim to online attacks that saw both web sites become unreachable," writes The Inquirer's Chris Martin. "According to Reuters, the attacks started on Monday evening and continued for at least 24 hours."

"Both companies said that although the web sites suffered disruption trading was not affected," Martin writes. "The origin of the attacks is unknown."

Go to "Nasdaq and Bats web sites are hit by a cyber attack" to read the details.

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