Yahoo! Assistant, formerly named 3721 Internet Assistant, is a Browser Helper Object for Internet Explorer developed by Beijing 3721 Technology Co. Ltd, and was renamed to Yahoo! Assistant after Beijing 3721 Technology was acquired by Yahoo!.
3721 Internet Assistant, together with 3721 Chinese Keywords, are known as Spyware by Microsoft AntiSpyware, and malware or browser hijacker by some others, such as Panda Antivirus. However, Yahoo! China filed a lawsuit against Beijing Sanjiwuxian Internet Technology Co. Ltd, the developer of the 360Safe antispyware for identifying Yahoo! Assistant as malware in 360Safe.
Read more about Yahoo! Assistant: Distribution, Features, Uninstall