Motorola buys network security firm

Schaumburg-based Motorola Inc., the biggest U.S. maker of mobile phones, agreed to buy AirDefense Inc., whose technology protects corporate wireless networks.

AirDefense, founded in 2001, makes software and equipment that shields corporate and government-agency networks secure from wireless threats, such as intrusion, Motorola said in a statement today. Terms of the transaction weren't disclosed.

AirDefense, based in Atlanta, will become part of the two- way radio business, whose customers include police departments, emergency personnel and corporations. Motorola plans to separate the radio and set-top box units from the money-losing handset- unit next year.

Motorola fell 17 cents, or 2.3 percent, to $7.08 at 4:15 p.m. in New York Stock Exchange composite trading. The shares have dropped 56 percent this year.

The deal should close in the next few months, Motorola said. The radio business accounted for about a fifth of Motorola's $36.6 billion in sales last year.