Qihoo 360

Just who is Qihoo? The firm is a leading provider of antivirus software and other Internet security products in China, a country that hosts the largest Internet user base in the world. Qihoo 360 Technology Co.'s flagship products include 360 Safe Guard and 360 Anti-Virus, programs that protect against malware and hacking and clean out processes and files to improve system performance. Other products include 360 Safe Browser (a popular Chinese Web browser) and 360 Mobile Safe (mobile security). The company earns most of its revenues from online advertising (offered via Web games developed by third parties) and value added services (such as remote technical support). Qihoo 360 filed to go public in 2011.