Understanding Email Headers: How to Detect and Prevent Email Spoofing
Email Spoofing is a deceptive tactic where attackers forge email headers to make messages appear as if they originate from trusted sources. This technique is commonly used in phishing attacks to deceive recipients into revealing sensitive information or downloading malicious software. Understanding how to analyze email headers can help you identify and protect against such fraudulent activities.
What Are Email Headers?
Email headers are essential components of an email message that contain vital information about its origin, route, and authenticity. They include fields such as ‘From’, ‘To’, ‘Subject’, ‘Date’, and several others that provide a trail of the email’s journey from sender to recipient. While some of these fields are visible in your email client, many are hidden and can be viewed by accessing the email’s source or original message.
How to Access Email Headers:
- Outlook: Open the email, click on “File,” then “Properties,” and view the “Internet headers” box.
- Gmail: Open the email, click on the three vertical dots next to the reply arrow, and select “Show original.”
- Yahoo Mail: Open the email, click on the three horizontal dots, and select “View raw message.”
Delivered-To: user@example.com
Received: by 2002:a17:902:5307:0:0:0:0 with SMTP id v7csp1452976ejw;
Wed, 03 Apr 2024 12:34:56 -0700 (PDT)
X-Received: by 2002:a1c:4b09:: with SMTP id g9mr1234567wma.67.1712172896123;
Wed, 03 Apr 2024 12:34:56 -0700 (PDT)
Return-Path: sender@domain.com
Received: from mail.domain.com (mail.domain.com. [123.45.67.89])
by mx.google.com with ESMTPS id b7si1234567qke.287.2024.04.03.12.34.56
for user@example.com
(version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256);
Wed, 03 Apr 2024 12:34:56 -0700 (PDT)
Received-SPF: pass (google.com: domain of sender@domain.com designates 123.45.67.89 as permitted sender) client-ip=123.45.67.89;
Authentication-Results: mx.google.com;
dkim=pass header.i=@domain.com header.s=selector1 header.b=abcd1234;
spf=pass (google.com: domain of sender@domain.com designates 123.45.67.89 as permitted sender) smtp.mailfrom=sender@domain.com;
dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=domain.com
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
d=domain.com; s=selector1; t=1712172896;
bh=VYgWqzXb1q83L9efk9EtqvL7W0U=;
h=Date:From:To:Subject:Message-ID;
b=abcd1234efgh5678ijkl9012mnop3456qrstuvwx…
Date: Wed, 3 Apr 2024 12:34:56 -0700
From: Sender Name sender@domain.com
To: Recipient Name user@example.com
Message-ID: CAJ1234567890abcdefg@mail.domain.com
Subject: Important Update on Your Subscription
MIME-Version: 1.0
Content-Type: text/plain; charset=”UTF-8″
Content-Transfer-Encoding: 7bit
Key Email Header Fields to Examine:
- From: Indicates the sender’s email address. However, this field can be easily forged and should not be solely relied upon to verify the sender’s identity.
- Reply-To: Specifies the email address to which replies should be sent. Discrepancies between the ‘From’ and ‘Reply-To’ addresses can be a red flag for spoofing.
- Received: Shows the servers that handled the email during its transmission. By examining the sequence of ‘Received’ fields, you can trace the path the email took and identify anomalies.
- Return-Path: Indicates where non-delivery receipts (bounces) are sent. A mismatch between the ‘Return-Path’ and ‘From’ addresses may suggest spoofing.
- Received-SPF: Displays the result of the Sender Policy Framework (SPF) check, which verifies if the email comes from an authorized server. A ‘Fail’ or ‘Softfail’ status can indicate potential spoofing.
Detecting Spoofed Emails:
- Examine the ‘Received’ Fields: Trace the email’s path by reviewing the ‘Received’ fields. Inconsistencies or unfamiliar server names can be indicators of spoofing.
- Check SPF, DKIM, and DMARC Results: These authentication mechanisms help verify the legitimacy of the email. Failures or absence of these checks can be warning signs.
- Analyze the ‘Return-Path’ and ‘Reply-To’ Fields: Ensure these fields match the ‘From’ address and are consistent with the sender’s domain.
- Use Email Header Analysis Tools: Online tools like MxToolbox’s Email Header Analyzer can simplify the process by parsing headers and highlighting issues.
By understanding and analyzing email headers, you can better detect and prevent email spoofing attempts, thereby safeguarding your personal and organizational security. Need extra security? Try ExchangeDefender PRO for free!