Question

Read RFC 5321 for SMTP. What does MTA stand for? Consider the following received spam email (modified from a real spam email). Assuming only the originator of this spam email is malacious and all other hosts are honest, identify the malacious host that has generated this spam email. From - Fri Nov 07 13:41:30 2008 Return-Path: Received: from barmail.cs.umass.edu (barmail.cs.umass.edu [128.119.240.3]) by cs.umass.edu (8.13.1/8.12.6) for ; Fri, 7 Nov 2008 13:27:10 -0500 Received: from asusus-4b96 (localhost [127.0.0.1]) by barmail.cs.umass.edu (Spam Firewall) for ; Fri, 7 Nov 2008 13:27:07 -0500 (EST) Received: from asusus-4b96 ([58.88.21.177]) by barmail.cs.umass.edu for ; Fri, 07 Nov 2008 13:27:07 -0500 (EST) Received: from [58.88.21.177] by inbnd55.exchangeddd.com; Sat, 8 Nov 2008 01:27:07 +0700 From: "Jonny" To: Subject: How to secure your savings

Short answer

MTA stands for Mail Transfer Agent. The malicious host is 'asusus-4b96' with IP [58.88.21.177].

Step-by-step solution

Identifying Components of the Email Header

First, we need to identify and understand the components of the email header. Email headers contain information about the path taken by the email from the sender to the receiver. The key parts are the 'Received' fields, which list the mail servers the message passed through. Each 'Received' line shows a transfer from one mail server to the next.

Analyzing the 'Received' Lines

The 'Received' lines are listed in reverse order of their appearance, meaning the first line shows the email's final destination. Analyze each 'Received' line from top to bottom to track its path from the first server to the final recipient. Look for discrepancies such as headers added by potentially malicious servers.

Identifying the Source of the Email

The email's first 'Received' line from the bottom originated from 'asusus-4b96 ([58.88.21.177])' before being passed to 'barmail.cs.umass.edu'. This suggests the host 'asusus-4b96' is the origin of the email. Look for any unusual IP addresses or host names that seem out of place compared to the others.

Comparing Host Information

Compare the IP addresses and hostnames. The 'asusus-4b96' machine, with IP address [58.88.21.177], does not match the trustworthy hosts like 'barmail.cs.umass.edu'. Since our assumption states the originator of the spam email is malicious, suspect this host ('asusus-4b96') is the source of the spam.

Key concepts

SMTP Protocol

The Simple Mail Transfer Protocol (SMTP) is a fundamental protocol used for sending emails over the internet. It has been the backbone of email communication since its inception. Understanding SMTP is crucial to comprehending how emails are transferred between servers.
SMTP works by establishing a secure connection between a sender and a recipient’s email server.
Here’s what typically happens:

• The sender's email client connects to an SMTP server using a specified port (usually port 25).
• Once connected, the client initiates a conversation using SMTP commands.
• The sender’s email server processes the commands and determines the recipient's server.
• The message is then forwarded to the recipient's server for delivery.

SMTP is like a post office that sorts and routes messages to their correct destination. Ensuring proper configuration and security in SMTP servers is vital to prevent the misuse of email systems, such as in spam emailing.

Email Header

An email header provides a wealth of information that can be incredibly useful for debugging, spam analysis, and understanding the journey an email has taken. The header contains

• "Received" lines;
• a "Return-Path" indicating the sender's email;
• and other details like timestamps and server names.

Analysis of email headers is a key step in tracing spam emails back to their origin. Each 'Received' line shows the path an email took across different servers. This information can help identify where the email originated and the sequence of servers it passed through. When analyzing email headers, it's important to start from the bottom-most 'Received' line since it reflects the earliest step in the email's journey.
The accuracy and honesty of the hosts can significantly influence the reliability of this information.

Mail Transfer Agent (MTA)

A Mail Transfer Agent (MTA) is a crucial component in the process of email delivery. It is responsible for accepting mails from a sender and forwarding them to the appropriate destination. An MTA functions similar to a postal sorting office,
where it sorts incoming mail and decides where each piece should go next.

• MTAs accept mail from client software.
• The software then forwards the message based on the recipient's address.
• They play a pivotal role in either local delivery or forwarding it further into the network.

MTAs are also responsible for managing email queues, retrying failed delivery attempts, and handling bounce-back messages when emails cannot be delivered. MTA logs can be studied to troubleshoot and diagnose mail routing issues, thereby playing a critical role in both legitimate email delivery and identifying spam sources.

IP Address Tracking

IP Address Tracking in email analysis is a valuable tool to trace the source of emails, especially useful in spam detection. By examining the IP addresses listed in the email headers, users can follow the trail an email has taken across various mail servers.
Here's how it works:

• Each email server that forwards an email stamps its own IP address onto the header.
• The headers can then be analyzed to track the path back to the message originator.
• Unusual or unrecognized IP addresses in the path can signify potential sources of spam.

Identifying the original sending server’s IP address may highlight discrepancies that allow investigators to spot spam emails. In the context of our spam example, examining the IP address '[58.88.21.177]' helped pinpoint the origin of the spam message.
IP tracking not only aids in spam analysis but also in cybersecurity efforts to trace malicious activities.