Barracuda Networks, a Campbell, Calif.-based maker of appliances to block spam and viruses transmitted over the web and email, announced that it bought a controlling interest in Austria-based Phion, a publicly-traded company that installs firewalls for enterprises, for about $18.7 million. Barracuda has been backed by Sequoia Capital and Francisco Partners, having raised $40 million in a 2006 first round of funding.