Apple buys companies like AuthenTec (AUTH), which according to an SEC 8-K filing Friday was picked up by Apple for $8 a share, a 58% premium over AuthenTec’s Thursday close of $5.07.

The Melbourne, Florida-based company makes fingerprint sensors and identity management software for PCs, tablets, smartphones, printers, network servers and other such devices. Among its customers are Samsung, the leading maker of Android devices, and Motorola, now a Google (GOOG) subsidiary.

Some reports have interpreted this as a shot against the bow of Samsung just before the big patent infringement trial that starts Monday.

But given that AuthenTec’s clients include Alcatel-Lucent, Cisco, Fujitsu, HBO, Hewlett-Packard, Lenovo, LG, Nokia, Orange, Sky, Texas Instruments and, apparently, the U.S. Army, it looks more to me as if Apple is getting serious about security.

UPDATE: According to Brian Marshall, AuthenTec has shipped over 100 million fingerprint sensors. In a note to clients he writes: “We view the deal as consistent with AAPL’s strategy to acquire technology assets it sees as important for product differentiation (e.g., C3 and Poly9 for mapping, Anobit for flash technology, Intrinsity and P.A. Semi for application processors, Siri for voice/language recognition, etc.).”