Reported via mail:
This is a new search engine in China called "360search".
// 360search
'so.360.cn' => array('360search', 'q', 's?q={k}', array('UTF-8', 'gb2312')),
'www.so.com' => array('360search', 'q', 's?q={k}', array('UTF-8', 'gb2312')),
Attachment:
favicon_360.png
(In [7389]) fixes #3521 added 360search as search engine