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Nmap Network Exploration and Security Auditing Cookbook, Third Edition

You're reading from   Nmap Network Exploration and Security Auditing Cookbook, Third Edition Network discovery and security scanning at your fingertips

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Product type Paperback
Published in Sep 2021
Publisher Packt
ISBN-13 9781838649357
Length 436 pages
Edition 3rd Edition
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Author (1):
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Paulino Calderon Paulino Calderon
Author Profile Icon Paulino Calderon
Paulino Calderon
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Table of Contents (22) Chapters Close

Preface 1. Chapter 1: Nmap Fundamentals 2. Chapter 2: Getting Familiar with Nmap's Family FREE CHAPTER 3. Chapter 3: Network Scanning 4. Chapter 4: Reconnaissance Tasks 5. Chapter 5: Scanning Web Servers 6. Chapter 6: Scanning Databases 7. Chapter 7: Scanning Mail Servers 8. Chapter 8: Scanning Windows Systems 9. Chapter 9: Scanning ICS/SCADA Systems 10. Chapter 10: Scanning Mainframes 11. Chapter 11: Optimizing Scans 12. Chapter 12: Generating Scan Reports 13. Chapter 13: Writing Your Own NSE Scripts 14. Chapter 14: Exploiting Vulnerabilities with the Nmap Scripting Engine 15. Other Books You May Enjoy Appendix A: HTTP, HTTP Pipelining, and Web Crawling Configuration Options 1. Appendix Β: Brute-Force Password Auditing Options 2. Appendix C: NSE Debugging 3. Appendix D: Additional Output Options 4. Appendix Ε: Introduction to Lua 5. Appendix F: References and Additional Reading

Detecting SMTP open relays

Open relays are insecure mail servers that allow third-party domains to use them without authorization. They are abused by spammers and phishers, and they present a serious risk to organizations because public spam blacklists may add the relay servers and affect an entire organization relying on email reaching their destinations.

This recipe shows how to detect SMTP open relays with Nmap.

How to do it...

Open your terminal and enter the following Nmap command:

$ nmap -sV --script smtp-open-relay -v <target>

The output returns the number of tests that passed if the SMTP server is an open relay, and the command combination used:

Host script results:
| smtp-open-relay: Server is an open relay (1/16 tests)
|_MAIL FROM:<[email protected]> -> RCPT TO:
<[email protected]>

How it works...

The smtp-open-relay script was submitted by Arturo Buanzo Busleiman, and it attempts 16 different tests to determine if an...

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