hacktricks/network-services-pentesting/7-tcp-udp-pentesting-echo.md

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# 基本信息

此主机上运行着一个回显服务。回显服务旨在用于测试和测量目的，可以监听TCP和UDP协议。服务器会原样发送接收到的任何数据。\
**通过将回显服务连接到同一台或另一台机器上的回显服务，可能会导致拒绝服务**。由于产生的数据包数量过多，受影响的机器可能会被有效地停止服务。\
信息来自[https://www.acunetix.com/vulnerabilities/web/echo-service-running/](https://www.acunetix.com/vulnerabilities/web/echo-service-running/)

**默认端口：** 7/tcp/udp
```
PORT   STATE SERVICE
7/udp  open  echo
7/tcp  open  echo
```
## 联系回显服务（UDP）

The Echo service is a simple network service that allows a client to send a message to the server, and the server will send the same message back to the client. This service is commonly used for testing and debugging network connectivity.

To contact the Echo service using UDP, you can use the `nc` command with the `-u` flag followed by the IP address and port number of the server. For example:

```
nc -u <server_ip> <port_number>
```

Replace `<server_ip>` with the IP address of the server running the Echo service, and `<port_number>` with the port number on which the service is listening.

Once the connection is established, you can send a message to the server, and it will echo the same message back to you. This can be useful for verifying that UDP packets are being properly transmitted and received.

Remember that UDP is a connectionless protocol, so there is no guarantee of delivery or order of packets. If you don't receive a response from the server, it could be due to network issues or firewall restrictions.

It's also worth noting that the Echo service is often disabled or restricted on production networks due to security concerns. Therefore, it's important to only use this service for testing purposes on authorized systems.
```bash
nc -uvn <IP> 7
Hello echo    #This is wat you send
Hello echo    #This is the response
```
## Shodan

* `port:7 echo`

# 参考资料

[Wikipedia echo](http://en.wikipedia.org/wiki/ECHO_protocol)

[CA-1996-01 UDP Port Denial-of-Service Attack](http://www.cert.org/advisories/CA-1996-01.html)


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