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After-hours buzz: Facebook, Plug Power & Ford

Check out which companies are making headlines after the bell Thursday:

Facebook - Shares of the social-networking site fell in extended-hours trading after news that the company was being sued over allegations it scanned private messages, according to a complaint filed in federal court in Northern California.

FireEye - The cybersecurity company reported fourth-quarter revenues that tops estimates and said it would buy Mandiant in a $1.05 billion cash-and-stock deal. Its shares rallied in after-hours trade.

Plug Power - Shares rose in extended-hours trade after the alternative energy company said it met its fourth-quarter order targets and projected first-quarter bookings would meet or exceed those of the prior quarter.

Ford - The auto manufacturer gained in after-hours trading on news it would show a concept version of an electric plug-in hybrid with a solar panel on the roof at a trade show next week.

—By CNBC's Kate Gibson.

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