判断是否被CC攻击的命令

使用下面的命令，可以分析下是否在被CC攻击。

## 第一条命令：
```
tcpdump -s0 -A -n -i any | grep -o -E '(GET|POST|HEAD) .*'
```
正常的输出结果类似于这样
```
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
```
正常命令结果以静态文件为主，比如css,js,各种图片。

如果是被攻击，会出现大量固定的地址，比如攻击的是首页，会有大量的“GET / HTTP/1.1”，或者有一定特征的地址，比如攻击的如果是Discuz论坛，那么可能会出现大量的“/thread-随机数字-1-1.html”这样的地址。

## 第二条命令：
```
tcpdump -s0 -A -n -i any | grep ^User-Agent
```
输出结果类似于下面：
```
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)
```
这个是查看客户端的useragent，正常的结果中，是各种各样的useragent。

大多数攻击使用的是固定的useragent，也就是会看到同一个useragent在刷屏。随机的useragent只见过一次，但是给搞成了类似于这样“axd5m8usy”，还是可以分辨出来。

## 第三条命令：
```
tcpdump -s0 -A -n -i any | grep ^Host
```
如果机器上的网站太多，可以用上面的命令找出是哪个网站在被大量请求

输出结果类似于下面这样
```
Host: www.server110.com
Host: www.server110.com
Host: www.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: www.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: www.server110.com
Host: www.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: www.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: www.server110.com
Host: www.server110.com
Host: www.server110.com
Host: www.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: www.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: www.server110.com
Host: www.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: www.server110.com
Host: upload.server110.com
Host: upload.server110.com
Host: www.server110.com
```
一般系统不会默认安装tcpdump命令

centos安装方法：`yum install -y tcpdump`

debian/ubuntu安装方法：`apt-get install -y tcpdump`