如何准确判断请求是搜索引擎爬虫发出的请求

去看网站日志，日志里面含有spider的一般都是搜索引擎爬虫发出的请求。另外，搜索引擎蜘蛛有真假，辨别方法 http://m.baidu.com/from=1001192k/bd_page_type=1/ssid=0/uid=0/pu=usm%401%2Csz%401320_1001%2Cta%40iphone_2_4.4_3_537/baiduid=5A220127E52AEEB073C96B1A9A1EBCFE/w=0_10_/t=iphone/l=1/tc?ref=www_iphone&lid=9897849017150079406&order=1&fm=alzd&tj=zhidao_1_0_10_l1&w_qd=IlPT2AEptyoA_ykxs4gpsBevEzpSk9K&sec=22882&di=843074725428cd02&bdenc=1&nsrc=IlPT2AEptyoA_yixCFOxXnANedT62v3IDBqMMS6LLDivpEmixP4kHREsRC0aNWiCGkb8gTCcshcJuXyd0m1l8B2CtKtjtmwh6SWhuKDhg_4MXw1OytIs_hOUHjMn9uir8xsv92xoP3Mo4GFufrqlrudbwvXJ82Qs-4yYeEOmnPaQWIDiWli&clk_info=%7B%22srcid%22%3A%2217%22%2C%22tplname%22%3A%22zhidao%22%2C%22t%22%3A1501496982573%2C%22sig%22%3A%225889%22%2C%22xpath%22%3A%22div-a-h3%22%7D