CC攻擊很容易發起，並且幾乎不需要成本，導致現在的CC攻擊越來越多。
大部分搞CC攻擊的人，都是用在網上下載的工具，這些工具很少去偽造特征，所以會留下一些痕跡。
使用下面的命令，可以分析下是否在被CC攻擊。
第一條命令：
tcpdump -s0 -A -n -i any | grep -o -E '(GET|POST|HEAD) .*'
正常的輸出結果類似於這樣
POST /ajax/validator.php HTTP/1.1
POST /api_redirect.php HTTP/1.1
GET /team/57085.html HTTP/1.1
POST /order/pay.php HTTP/1.1
GET /static/goodsimg/20140324/1_47.jpg HTTP/1.1
GET /static/theme/qq/css/index.css HTTP/1.1
GET /static/js/index.js HTTP/1.1
GET /static/js/customize.js HTTP/1.1
GET /ajax/loginjs.php?type=topbar& HTTP/1.1
GET /static/js/jquery.js HTTP/1.1
GET /ajax/load_team_time.php?team_id=57085 HTTP/1.1
GET /static/theme/qq/css/index.css HTTP/1.1
GET /static/js/lazyload/jquery.lazyload.min.js HTTP/1.1
GET /static/js/MSIE.PNG.js HTTP/1.1
GET /static/js/index.js HTTP/1.1
GET /static/js/customize.js HTTP/1.1
GET /ajax/loginjs.php?type=topbar& HTTP/1.1
GET /static/theme/qq/css/i/logo.jpg HTTP/1.1
GET /static/theme/qq/css/i/logos.png HTTP/1.1
GET /static/theme/qq/css/i/hot.gif HTTP/1.1
GET /static/theme/qq/css/i/brand.gif HTTP/1.1
GET /static/theme/qq/css/i/new.gif HTTP/1.1
GET /static/js/jquery.js HTTP/1.1
GET /static/theme/qq/css/i/logo.jpg HTTP/1.1
正常命令結果以靜態文件為主，比如css,js,各種圖片。
如果是被攻擊，會出現大量固定的地址，比如攻擊的是首頁，會有大量的“GET / HTTP/1.1”，或者有一定特征的地址，比如攻擊的如何是Discuz論壇，那麼可能會出現大量的“/thread-隨機數字-1-1.html”這樣的地址。
第二條命令：
tcpdump -s0 -A -n -i any | grep ^User-Agent
輸出結果類似於下面：
User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0)
User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0)
User-Agent: Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.89 Safari/537.1
User-Agent: Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.89 Safari/537.1
User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0)
User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0)
User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0)
User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0)
User-Agent: Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.89 Safari/537.1
User-Agent: Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.89 Safari/537.1
User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Trident/4.0; .NET CLR 2.0.50727; 360space)
User-Agent: Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.89 Safari/537.1
User-Agent: Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.89 Safari/537.1
User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; Trident/4.0; .NET CLR 2.0.50727; 360space)
User-Agent: Mozilla/5.0 (compatible; bingbot/2.0; +http://www.bing.com/bingbot.htm)
User-Agent: Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.89 Safari/537.1
User-Agent: Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.89 Safari/537.1
User-Agent: Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.89 Safari/537.1
User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0)
User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0)
User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0)
User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0)
User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0)
User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0)
User-Agent: Mozilla/5.0 (Windows NT 5.1) AppleWebKit/537.1 (KHTML, like Gecko) Chrome/21.0.1180.89 Safari/537.1
User-Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0)
User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0)
User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0)
User-Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; .NET CLR 2.0.50727; InfoPath.2)
User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0)
這個是查看客戶端的useragent，正常的結果中，是各種各樣的useragent。
大多數攻擊使用的是固定的useragent，也就是會看到同一個useragent在刷屏。隨機的useragent只見過一次，但是給搞成了類似於這樣“axd5m8usy”，還是可以分辨出來。
第三條命令：
tcpdump -s0 -A -n -i any | grep ^Host
如果機器上的網站太多，可以用上面的命令找出是哪個網站在被大量請求
輸出結果類似於下面這樣
Host: www.45it.com
Host: www.45it.com
Host: www.45it.com
Host: sos.45it.com
Host: sos.45it.com
Host: sos.45it.com
Host: sos.45it.com
Host: sos.45it.com
Host: sos.45it.com
Host: sos.45it.com
Host: sos.45it.com
Host: sos.45it.com
Host: www.45it.com
Host: sos.45it.com
Host: sos.45it.com
Host: sos.45it.com
Host: www.45it.com
Host: www.45it.com
Host: sos.45it.com
Host: sos.45it.com
Host: sos.45it.com
Host: www.45it.com
Host: sos.45it.com
Host: sos.45it.com
Host: www.45it.com
一般系統不會默認安裝tcpdump命令
centos安裝方法：yum install -y tcpdump
debian/ubuntu安裝方法：apt-get install -y tcpdump
很多小白用戶不懂得如何設置日志，查看日志，使用上面的命令則簡單的多，復制到命令行上運行即可。
