While you're getting ready to watch the NCAA tournament security firms are watching what fans are tweeting. Companies monitor online chatter before a game to help them make decisions about how many security officers to send to a venue. They look for indications that fans plan on storming the court or blocking streets - like these University of Dayton fans after their team's big win over Syracuse. Police departments have been monitoring Twitter, Facebook and Instagram to look for possible criminal activity for some time.
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