How to Forge email

最新推荐文章于 2025-11-09 12:07:49 发布

转载最新推荐文章于 2025-11-09 12:07:49 发布 · 1.8k 阅读

文章标签：

#email #server #warnings #internet #command #authentication

Security 专栏收录该内容

22 篇文章

订阅专栏

本文介绍如何利用开放中继的SMTP服务器伪造发件人的电子邮件地址。通过使用telnet命令连接到允许转发邮件的服务器，并输入特定的SMTP命令，可以发送看似来自任意第三方地址的邮件。

How to Forge Email

SMTP, or Simple Mail Transport Protocol, is the name of the method computers use to send mail to each other, in other words SMTP is the language mail servers on the Internet use to speak to each other. Until the mid-1990's the default configuration for SMTP servers was to allow email forwarding, to act as a relay, which allowed people to use their own email address from almost any network location. Spammers soon caught on as this allowed them to send masses of commercial emails that did not appear to originate from their severs, and as a result the forwarding ability to most SMTP servers was turned off. Today fewer than 1% of SMTP servers allow mail forwarding, and many ISPs and email providers will not accept mail from these machines. Today you can still use SMTP forwarding if you can find a SMTP server that allows it. In this wikiHow we'll look at how you can use an open relay to send email that appears to originate form any third party address you choose.

[Steps]

Open a command prompt by clicking Start, Run, and type cmd in the box and press OK. You should get a black "Command Prompt" screen.
- This can be done with the Terminal.app in Macintosh OS X and the command line in most Unix and Linux based operating systems.
Find out the name of your ISP's mail server, normally mail.isp.com or smtp.isp.com. This should be in your email client settings.
Type telnet mail.isp.com 25. 25 is the port number most SMTP servers use. Learn more about telnet.
When the mail server responds, you can start typing SMTP commands.
Start with HELO blahblah.isp.com. You may have to use your ISP's domain name for it to be accepted.
If it says 'pleased to meet you' or something like that, continue with the address you want the mail to come FROM. So, to forge mail from Bill Gates, type MAIL FROM: billg@microsoft.com.
If it says Sender OK, type who you want the mail to go to, i.e. your friends address. Type RCPT TO: yourfriend@isp.com
If it says Recipient OK, then you can type your message:
1. Type DATA and press Enter.
2. On the first line type Subject: yoursubject and press Enter twice.
3. Continue typing your message, such as 'I'm bill gates and want to send you a billion dollars'.
4. Put a single period (.) on a line by itself and press Enter to send your message. The server should say 'Message accepted for delivery'.
You are done. You have just forged an email, and the recipient should be receiving it shortly.
You can test to see if a given SMTP server is configured for forwarding by using online tools.

[Tips]

if you do not see the letters you type in your terminal application use the echo command.
Practice sending the message to yourself a few times until you get the hang of it.
Send it to yourself and view all the headers to make sure nothing that easily identifies you as the sender (like your computer name) shows up.
Servers which run enhanced SMTP will also accept 'ehlo blahblah.isp.com'. You may still need to use your ISP's domain name for it to be accepted.
It is normally easier just to find one of the many free websites that will allow you to send emails to anyone from anyone.
As mentioned in the warnings, most SMTP servers have relaying disabled. Many times you can overcome this by connecting to the ISP of the target email, since the server will accept it as a "local delivery" - i.e., if the target's address is "joe@company.com" telnet to "company.com" and forge it from there. Most "@company.com" mail servers are either "company.com", "mail.company.com" or "smtp.company.com".
If you use Windows telnet client and make a spelling mistake do not use the backspace key, instead, press ^] (CTRL+RIGHT BRACKET) to terminate the connection and try again. The backspace key is transmitted incorrectly and will result in odd characters appearing in the final message.
Some individuals believe running an open relay is a free speech issue, including John Gilmore, a long time Internet "personality" and one of the founders of the The Electronic Frontier Foundation. As a result most ISPs do not accept mail from Gilmore's servers.

[Warnings]

This method of forging email may not work at times. Almost all Internet service providers' SMTP servers and some private SMTP servers require authentication before permitting email to be sent. You can manually authenticate with an SMTP server, but you'll need to read RFC 2554 to learn how. Also, an SMTP server will generally only relay a message if it is either FROM or TO an address with the same domain name as its own.
This is not a foolproof method of sending anonymous email. Only a small amount of effort is required for a diligent party to positively identify you as the sender.
All that your ISP and law enforcement needs to do is look at the email headers and see the date/time and IP address the message came from. You can then be held accountable for any harm you may have caused by your email.
Some U.S. states now have laws against fraudulent email, especially when tied to a commercial endeavor. Be aware of any legal ramifications of your actions.