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Nmap Network Scanning 125

brothke writes "The 1962 song Wipe Out, with its energetic drum solo started, was the impetus for many people to take up playing the drums. Similarly, Nmap, the legendary network scanner, likely interested many in the art of hacking, and for some, started a career for security professionals and hackers. Nmap and its creator Fyodor need no introduction to anyone on Slashdot. With that, Nmap Network Scanning: The Official Nmap Project Guide to Network Discovery and Security Scanning, is a most useful guide to anyone interested in fully utilizing Nmap." Read on for the rest of Ben's review.
Nmap Network Scanning: The Official Nmap Project Guide to Network Discovery and Security Scanning
author Gordon Lyon (Fyodor)
pages 468
publisher Nmap Project
rating 9
reviewer Ben Rothke
ISBN 978-0979958717
summary Valuable book about an invaluable security tool
One may ask, why spend $50 on this book, when the Nmap Reference Guide provides a significant amount of the basic information needed to use the tool, especially since the reference guide is both free, and well written. The reference guide is included in the book in chapter 15, and takes up 41 pages. And for those that are cash strapped, the free reference guide is the way to go.

In addition, the web site for the book notes that about half of the content is available in the free online edition. The most useful information is in the book in chapters exclusive to the print edition, which includes Detecting and Subverting Firewalls and Intrusion Detection System, Optimizing Nmap Performance, Port Scanning Techniques and Algorithms, Host Discovery, and troubleshooting.

The main benefit of the buying the book is that it has the collected wisdom of Fyodor's, in addition to numerous real-world scenarios, and Nmap commands not documented elsewhere. At over 400 pages, the books 15 chapters provide the reader with everything they need to know about using Nmap to the fullest.

Chapter 1 starts with an overview of the history of Nmap and how it came to be. As to the question of whether port scanning is legal, the author writes that it is best to avoid the debate and its associated analogies. He advises that it's best to avoid ISP abuse reports and criminal charges, by not annoying the target network administrators in the first place. Chapter 1 provides a number of practical suggestions on just how to do that.

A complaint against Nmap it that is has often been blamed for crashing systems. Chapter 1 shows that the reality is that Nmap will rarely be the primary cause of a system crash. The truth is that many of the systems that crashed as a result of an Nmap scan were likely unstable from the outset, and Nmap either pushed them over the top or they coincidentally crashed at the same time as the Nmap scan.

An ironic incident detailed in chapter 3 is when someone from the information security department of Target Corp. complained to the author that he felt the Nmap documentation was particularly directed at his organization; given the use of the term target. He requested that the Nmap documentation be changed from targetto example. The section on target enumeration in the book shows the author did not take that request to heart.

Another example of where the book goes beyond what is in the reference guide is where the author shows the most valuable TCP ports via his probe of tens of millions of IP addresses across the internet. Not surprisingly, ports 80 23 and 443 were the top three most commonly open TCP ports. It is surprising that other ports, which should have been secured long ago, are still as vulnerable as ever.

For the serious Nmap user, the book is worth purchasing just for the indispensable information in chapter 16, which is about optimizing Nmap performance. The author writes that one of his highest priorities in the creation of Nmap has been performance. Nmap uses parallelism and numerous advanced algorithms to execute its blazingly fast scans. This chapter shows how to create Nmap commands to obtain only the information you care about and significantly sped up the scan. The chapter details numerous scan time reduction techniques, and strategies on how to deal with long scans. The chapter concludes with the output of a user who, with a customized Nmap command, was able to reduce his scan of a 676,352 IP address network from nearly a week to 46 hours.

Chapter 10 is also a fascinating chapter on the topic of detection and subverting of firewalls and IDS. The function of such tests on an internal network is to help an organization understand the dangers and risks of a real attack. Since it is not uncommon for firewalls to be accidentally misconfigured, or have rule bases that leak from far too many rules; such a test can be quite useful to any network.

Nmap Network Scanning: The Official Nmap Project Guide to Network Discovery and Security Scanning is the guide for anyone who wants to get more out of Nmap. It is useful whether one is a novice and only getting into basic security testing, or an advanced user looking for ways to optimize Nmap.

The book takes a real-world approach on how to use the tool and clearly documents every Nmap feature and option. It also shows how the tool should be correctly used in various settings.

What is unique about is that this is a rare book in which the creator of the program wrote it. Linus Torvalds never got around to writing a Linux reference, nor did the creators of the Check Point firewall. In Nmap Network Scanning, the reader gets the story from the creator of the code itself. This then is the ultimate Nmap reference guide.

Aside from the history and use of the program in the first chapter, the rest of the book is an extreme guide to maximizing the use of Nmap. It is written by a programmer and written for the technically astute. Anyone who wants to maximize their use of Nmap will find no better reference.

Ben Rothke manages the Bright Hub Enterprise Security channel and is the author of Computer Security: 20 Things Every Employee Should Know.

You can purchase Nmap Network Scanning: The Official Nmap Project Guide to Network Discovery and Security Scanning from Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.


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Nmap Network Scanning

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  • by kwabbles ( 259554 ) on Monday December 08, 2008 @03:12PM (#26037345)

    I always roll my eyes when I hear someone complain about nmap "crashing a system". This should be common sense. If the target crashed simply from being nmapped or scanned from the outside - the target is obviously a turd of a system.

  • Re:In college... (Score:5, Insightful)

    by russotto ( 537200 ) on Monday December 08, 2008 @03:48PM (#26037901) Journal

    The Internet doesn't work if you need permission to send an IP packet to someone.

  • by LingNoi ( 1066278 ) on Monday December 08, 2008 @04:20PM (#26038399)

    I have no other words for this apart from, "What the fuck?"

  • by fuzzyfuzzyfungus ( 1223518 ) on Monday December 08, 2008 @04:38PM (#26038609) Journal
    That is because you are thinking like an engineer and they aren't. People, even people who should know better, have perverse attitudes about problems.

    Somebody at the meeting has some concerns about the viability of the plan. Praise him for voicing those concerns so that they can, if necessary, be addressed? Heck no, tell that whiner that there is no place for negativity among team players.

    Nmap crashes the system. Great, we discovered a DOS vulnerability before it could be used against us? Hardly, if that hacker hadn't been hacking none of this trouble would have happened.

    I'm not sure how much of this is just laziness: If the problem doesn't show up on my watch it isn't my problem; and how much is actual magical thinking. A disturbing number of people seem to think that optimism actually makes things work, pessimism actually breaks things, negativity actually makes things work, etc. The Secret [] is perhaps the purest form of this utter nonsense; but slightly milder variants are all over the place.
  • by kwabbles ( 259554 ) on Monday December 08, 2008 @05:07PM (#26039005)

    The kicker was the 150 hours of community service I had to put in to pay for the time (of 'computer professionals' who were worth a lot more money than I was) it took to bring them back online.

    And just think - since most likely all they had to do was reboot the damned things, what you were really putting in your "sweat equity" to pay for was their time to go back and fix their own mistakes, since they obviously hadn't done their jobs right in the first place.

    However, this brings up an important rule of thumb: Don't pen test something that you don't have permission to pen test, unless you've accepted that you will be prosecuted if caught. There are a lot of idiot admins out there watching their logs ready to point fingers the moment they see a port scan... not because they're concerned about security, but because "hackers" make excellent scapegoats for incompetent admins.

  • Re:In college... (Score:3, Insightful)

    by magarity ( 164372 ) on Monday December 08, 2008 @08:47PM (#26041851)

    my school's IT department confused my port scanning with that of a virus
    At a consulting client once I plugged in my usb thumb drive to transfer a document and the corporate scanning software on their computer detected nmap. It was immediately deleted with a pop-up that screamed "hacking tool detected!" On the one hand I was glad I didn't get escorted out (and not paid) but on the other hand it was rude of them to delete it when they could have just disallowed running it.

  • by dbIII ( 701233 ) on Monday December 08, 2008 @10:12PM (#26042483)
    Some HP printers and network to parallel port converters fit squarely into that catagory on all accounts but are still expensive things to fix after a port scan.
  • by Surreal Puppet ( 1408635 ) on Tuesday December 09, 2008 @10:36AM (#26046273) Journal

    The source is right there for you to read. Also, he's not the only guy working on the project, lots of other people have reviewed the code. Anything fishy would have been caught a long time ago.

"The way of the world is to praise dead saints and prosecute live ones." -- Nathaniel Howe