Q11 Email Forgery Flashcards
(1 cards)
Which of the following parts of an email cannot be forged? Explain why.
* Sender email address
* Subject line
* Sender IP address
* Content
* Headers including date, time, etc
* Recipient email address at RCPT TO field
Email Parts and Forgery:
Based on the sources, particularly the discussion on email spoofing and the structure of emails and SMTP:
* Sender email address: Can be forged. The “From” header in the email message is easily set by the sender, and the SMTP protocol’s MAIL FROM command (in the envelope) does not have inherent authentication, allowing it to be set arbitrarily by the sending server.
* Subject line: Can be forged. This is part of the email header and can be set to anything by the sender.
* Sender IP address: Can be forged in certain headers (like arbitrary X-Originating-IP headers). However, the IP address the connection actually came from is typically recorded by the receiving mail server in a Received: header. While a compromised sending server might hide the true original client IP, the IP of the server that connected is logged by the next hop. So, while the IP presented in the message can be fake, the IP logged by legitimate receiving servers in the transport path is harder for the sender to falsify reliably across multiple hops. The source implies spoofing is easy due to lack of authentication, which applies to originating IP claims as well.
* Content: Can be forged. This is the body of the email and is entirely controlled by the sender.
* Headers including date, time, etc: Generally can be forged. Most standard headers (Date, To, Cc, etc.) can be set by the sender. However, the chain of Received: headers added by each Mail Transport Agent (MTA) that processes the email is difficult for the original sender to completely forge as a consistent, verifiable history. Each MTA adds its own Received: header noting the time, date, and source of the incoming connection. While the first header might be controlled by a malicious sender’s server, subsequent headers added by uncompromised servers act as a log.
* Recipient email address at RCPT TO field: Likely cannot be forged by simply crafting the message content in a way that fools the delivery system. This field is part of the SMTP envelope commands used during the conversation between MTAs to specify the actual recipient(s) for delivery. Unlike headers, which are data within the email message file, RCPT TO is a protocol instruction processed by the receiving MTA to determine where to send the email. An attacker crafting an email message file cannot arbitrarily insert a fake RCPT TO command into the delivery stream processed by legitimate intermediate MTAs. It’s controlled by the MTA initiating the connection based on its routing logic.
Conclusion (Based on Sources): Sender email address, Subject line, Content, and most arbitrary Headers can be easily forged due to the lack of authentication in core protocols. The chain of Received: headers added by legitimate intermediate servers is difficult for the sender to fake entirely. The Recipient email address at RCPT TO field, being an envelope command processed by MTAs for transport, is fundamentally different from header fields and is not typically something a sender can arbitrarily forge by crafting the message content to misdirect delivery via uncompromised servers.
