监控系统状态

抓包工具 tcpdump

用法：tcpdump -nn

tcpdump -nn -i ens33

tcpdump -nn port 80

tcpdump -nn not port 22 and host 192.168.0.100

tcpdump -nn -c 100 -w 1.cap

tshark -n -t a -R http.request -T fields -e "frame.time" -e "ip.src" -e "http.host" -e "http.request.method" -e "http.request.uri"

yum install -y wireshark

tcpdump命令

tcpdump命令，是用来抓包的

安装tcpdump包——>yum install -y tcpdump

tcp -nn -i eno16777736

第一个n，表示你的ip用数字的形式显示出来(若是不加，则会显示出主机名)

[root@hf-01 ~]# tcpdump -nn

tcpdump: packet printing is not supported for link type NFLOG: use -w

[root@hf-01 ~]# ifconfig

eno16777736: flags=4163 mtu 1500

inet 192.168.74.129 netmask 255.255.255.0 broadcast 192.168.74.255

inet6 fe80::20c:29ff:feff:fe93 prefixlen 64 scopeid 0x20

ether 00:0c:29:ff:fe:93 txqueuelen 1000 (Ethernet)

RX packets 11067 bytes 12250186 (11.6 MiB)

RX errors 0 dropped 0 overruns 0 frame 0

TX packets 2631 bytes 312427 (305.1 KiB)

TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

lo: flags=73 mtu 65536

inet 127.0.0.1 netmask 255.0.0.0

inet6 ::1 prefixlen 128 scopeid 0x10

loop txqueuelen 0 (Local Loopback)

RX packets 0 bytes 0 (0.0 B)

RX errors 0 dropped 0 overruns 0 frame 0

TX packets 0 bytes 0 (0.0 B)

TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

[root@hf-01 ~]# tcpdump -nn -i eno16777736

5204, ack 6605, win 159, length 180

06:27:41.186368 IP 192.168.74.129.22 > 192.168.74.1.49322: Flags [P.], seq 45955204:45955384, ack 6605, win 159, length 180

06:27:41.186422 IP 192.168.74.129.22 > 192.168.74.1.49322: Flags [P.], seq 45955384:45955564, ack 6605, win 159, length 180

等等等，运行后，会显示出很多的信息

按ctrl+c退出

DDos攻击

udp flood叫udp的洪水攻击

在遇到这种攻击的时候，只能接入防攻击的设备(比如：创宇--300G是可以顶住的)

tcpdump命令指定端口

tcpdump -nn -i eno16777736 port 22

[root@hf-01 ~]# tcpdump -nn -i eno16777736 port 22

4, length 0

06:52:04.034073 IP 192.168.74.129.22 > 192.168.74.1.49322: Flags [P.], seq 228004:228376, ack 1, win 159, length 372

06:52:04.034155 IP 192.168.74.129.22 > 192.168.74.1.49322: Flags [P.], seq 228376:228556, ack 1, win 159, length 180

06:52:04.034302 IP 192.168.74.1.49322 > 192.168.74.129.22: Flags [.], ack 228556, win 252, length 0

06:52:04.034387 IP 192.168.74.129.22 > 192.168.74.1.49322: Flags [P.], seq 228556:228832, ack 1, win 159, length 276

等等等，只截取了一部分

tcpdump命令使用排除法

tcpdump -nn not port 22 and host 192.168.0.100 除去22端口和只要ip为192.168.0.100的包

tcpdump命令指定长度和个数

tcpdump -nn -i eno16777736 -c 100 -w 1.cap 指定数据包只要10个，并存入到1.cap文件中去

在终端查看的时候，不产生一些数据量的话，就不会产生那么多数据包

file 1.cap 查看该文件——>文件名称可以随意更改

能查看文件的大概信息

该文件不能直接 cat命令 查看的，会出现乱码

因为1.cap这个文件就是从你网卡里捕捉到的数据包，就是你通信的那个数据

在这里复制另一个终端，并打开，跑vmstat 1命令

在当前终端查看，输入以下命令

[root@hf-01 ~]# tcpdump -nn -i eno16777736 -c 10 -w 1.cap

tcpdump: listening on eno16777736, link-type EN10MB (Ethernet), capture size 262144 bytes

10 packets captured

10 packets received by filter

0 packets dropped by kernel

[root@hf-01 ~]# file 1.cap

1.cap: tcpdump capture file (little-endian) - version 2.4 (Ethernet, capture length 262144)

[root@hf-01 ~]#

若要查看这个文件，则可以tcpdump -r 1.cap

-r 表示读

[root@hf-01 ~]# tcpdump -r 1.cap //查看1.cap文件

reading from file 1.cap, link-type EN10MB (Ethernet)

07:02:05.134302 IP 192.168.74.129.ssh > 192.168.74.1.49322: Flags [P.], seq 4218852344:4218852492, ack 3076966380, win 159, length 148

07:02:05.134859 IP 192.168.74.1.49322 > 192.168.74.129.ssh: Flags [.], ack 148, win 255, length 0

07:02:05.257655 IP 192.168.74.129.ssh > 192.168.74.1.49322: Flags [P.], seq 148:280, ack 1, win 159, length 132

07:02:05.462113 IP 192.168.74.1.49322 > 192.168.74.129.ssh: Flags [.], ack 280, win 255, length 0

07:02:06.258704 IP 192.168.74.129.ssh > 192.168.74.1.49322: Flags [P.], seq 280:428, ack 1, win 159, length 148

07:02:06.462164 IP 192.168.74.1.49322 > 192.168.74.129.ssh: Flags [.], ack 428, win 254, length 0

07:02:07.259714 IP 192.168.74.129.ssh > 192.168.74.1.49322: Flags [P.], seq 428:560, ack 1, win 159, length 132

07:02:07.460218 IP 192.168.74.1.49322 > 192.168.74.129.ssh: Flags [.], ack 560, win 254, length 0

07:02:08.260717 IP 192.168.74.129.ssh > 192.168.74.1.49322: Flags [P.], seq 560:708, ack 1, win 159, length 148

07:02:08.460263 IP 192.168.74.1.49322 > 192.168.74.129.ssh: Flags [.], ack 708, win 253, length 0

[root@hf-01 ~]#

在read的返回的时候，是数据流，从哪到哪(包括tcpdump -nn屏幕上显示的也是数据流)

而tcpdump -r的时候，写入的是真正的数据包

tshark命令

tshark命令

安装tshark包——>yum install -y wireshark

tshark和tcpdump类似的工具，也是用来抓包的

tshark -n -t a -R http.request -T fields -e "frame.time" -e "ip.src" -e "http.host" -e "http.request.method" -e "http.request.uri" 查看指定网卡，80端口的一个web访问情况

类似于web的访问日志