(Updates with Cisco's closing stock price)

NEW YORK ( TheStreet) -- Cisco ( CSCO) sticks to the acquisition path with a $183 million all-cash purchase of closely held ScanSafe, its third deal in the past month.

ScanSafe makes network-based security software for businesses looking to manage data connections between offices and workers. The company, based in San Francisco and London, was founded in 1999 by two investment banking brothers, Eldar and Roy Tuvey.

ScanSafe has 150 employees and includes Google ( GOOG), AT&T ( T) and Sprint ( S) among its customers. ScanSafe is among a roster of companies that make so-called software-as-a-service products that provide service from the network or cloud instead of applications installed on computers.

Cisco says it plans to add ScanSafe security and filtering products to its virtual private network services.

Earlier this month, Cisco agreed to acquire Norwegian video-conferencing specialist Tandberg for $3 billion. And two weeks ago, Cisco made a $2.9 billion deal for wireless gearmaker Starent ( STAR).

Despite the recent flurry of activity, ScanSafe is only Cisco's sixth acquisition of the year, one more than last year, but lagging its 11 acquisitions in 2007.

Cisco shares ended Tuesday's trading session down 0.7% to $23.54.