为什么不能伪造IP地址？ [英] Why is it not possible to fake an IP address?

问题描述

我知道可以使用代理更改IP地址，但我很感兴趣为什么不能通过从单台计算机发送更改的数据来更改它？

I know it's possible to change an IP address using a proxy, but I'm interested in why is it not possible to change it by sending changed data from a single computer?

更新：

感谢您快速回复，但不清楚，如果使用无状态协议会发生什么，例如HTTP。我不熟悉较低级别的网络通信，但理论上，如果PC连接到服务器并立即收到回复，理论上应该可以获取IP地址。

Thanks for quick replies, but it's not clear, what would happen, should a stateless protocol be used, like HTTP. I'm not familiar with lower-level network communication, but it seems that theoretically it should be possible to faken IP address if a PC connects to the server and receives the reply immediately.

推荐答案

完全可以使用虚假的发件人IP发送数据。你会很难得到回复，因为回复将被发送到虚假的IP，永远不会到达你。此外，如果您使用路由器不希望从您那里获得的来自IP发送数据，路由器通常会丢弃它，有时会通知ISP您违反了您的服务条款。

It is fully possible to send data with a fake sender IP. You'll have a hard time getting replies though, since the replies will be sent to the fake IP and never reach you. Additionally, if you send data with a "from" IP that a router doesn't expect to arrive from you, the router will often simply drop it, and sometimes inform the ISP that you're up to something that violates your TOS.

编辑：回复编辑的帖子。

In response to edited post.

建立在上面的任何协议（例如HTTP）面向连接的协议（TCP）将需要有效的IP。伪造IP普遍存在的情况主要涉及拒绝服务攻击，在TCP握手中使用UDP，ICMP或初始SYN数据包。

Any protocol (such as HTTP) that is built on top of a connection-oriented protocol (TCP) will require a valid IP. The cases where fake IPs have been prevalent mostly involve Denial Of Service attacks, using UDP, ICMP or the initial SYN packet in a TCP handshake.

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