Customer Reviews

Silence on the Wire: A Field Guide to Passive Reconnaissance and Indirect Attacks

5 star:		(16)
4 star:		(7)
3 star:		(2)
2 star:		(0)
1 star:		(1)

 

 

If you have been a senior technical analyst in an infosec shop for several year, you have seen most of this before, in fact some of it has been published before. However, I have never seen so much information in one place on the subject of passive reconnaissance. Who needs horror movies? Read this book and follow it up with Black Ice by Verton and you probably will not sleep for a week!

If you work in information warfare, this should be mandatory reading! If you are responsible for very high value targets like Walmart's dataprocessing, or Intel's or Citibank's it is imperative that you read Zalewski's work page by page.

I don't think the book will work for those new to networking and technical security. It almost could but the book's layout reads more like a thesis, or an IEEE journal paper than a helpful book that teaches and equips. I do this stuff for a living and had to stop several times and say, "OK what is the point".

If this goes to second printing or second edition, I recommend the use of tools such as text boxes and callouts to make the main points easier to follow.

Chapter 9 was the biggest disappointment. The author is truly an expert and could have taught the reader so much more about the interpretation of the header fields.

However, those are nits, no book can be perfect. The book is well worth the money for the right reader! I am glad I got to read it and will recommend it for the SANS conference book store!

I received Silence on the Wire (SOTW) almost one year ago. When I first tried reading the book, I couldn't get past Ch 1. In fact, I didn't try reading anything for three months, hoping I could re-engage SOTW. Eventually I put SOTW aside and read other books, only to return to SOTW this week. I'm glad I gave SOTW a second chance. There's plenty to like in this book if you look for the details that interest you.

Don't get me wrong; SOTW is one of the most innovative and original computing books available. You will find it even more interesting if you are not familiar with many of the works the author summarizes or describes. Those of you who have been active for the last 5-10 years will recognize research on poor Initial Sequence Numbers, various timing attacks, remotely counting hosts behind NAT, and so on. In some cases the author added novel insights to this old research, or presented related but obscure new variations. NAT detection via MSS clamping (Ch 11) is one example.

In some cases the author describes really cool techniques based on research I had not encountered. Parasitic storage and getting remote hosts to solve computational problems (Ch 16) are amazing ideas. Kudos to the author for including a bibliography, with references to many interesting papers.

SOTW suffers from one major flaw. SOTW sometimes wastes far too much time getting to "the point." For example, Ch 2 spends 20 pages explaining internal CPU workings and logic gates before finally talking about timing attacks. This bothered me on two fronts. One, many readers do not need a rehash of computing basics. Two, I was less inclined to slog through those 20 pages because I did not know why they were included.

This tendency to spend far too much time on background material appears in other SOTW chapters. Ch 5 spends 15 pages on modems and Ethernet before getting to "the point." (Ch 6 also repeats Ethernet basics.) Ch 9 includes way to many pages describing IP, UDP, TCP, and ICMP headers -- basic data found in any introductory networking book. Ch 14 describes the Web, HTTP, cookies, etc. The truth is that computing newbies are not going to appreciate many deeper insights in SOTW. If one accepts the premise that the audience must be intermediate-advanced to like the book, why waste their time on basic material?

I found only a few minor flaws. First, the author repeatedly starts sentences with "Too,". That should have been edited out. Second, p 80 states that "20 meters" is "just under 100 feet". It's more like 66 feet. On p 194 we read that sending a SYN packet to a closed port elicits a "RST". I see this frequently in networking books, which is frustrating; a SYN to a closed port elicits a RST ACK. (The authors uses the correct terminology later in the book, however.) On pp 130-131 the text and a table claims that TCP sequence numbers are "echoed back" in the SYN ACK and ACK segments. This isn't the case, as the numbers are incremented, not echoed. On p 129 the author repeats the claim that Kevin Mitnick used a TCP spoofing attacking against Tsutomo Shimomura, although that is most likely not true.

Overall, SOTW is a fascinating book. The intended audience will probably find it most rewarding to skim the text for valuable insights, and skip details on the basics of VLANs, STP, DTP, and the like. On a philosophical level, SOTW's frequent invocation of Turing and other luminaries reminded me that computer science is not the same as computer operations. Universities that churn out computer scientists are producing students not likely able to cope with the reality of intruders exploiting methods outlined in SOTW.

Irrespective of the myriad proclamations of systems or products being hackerproof, bulletproof and the like; given enough time and money, everything is breakable. Security purists may argue that one-time pads are provably and perfectly secure. While that is correct in the pristine halls of academic cryptography, the real world is littered with many one-time pads of dubious security.

The fact that everything is breakable from an information security perspective is good news to Luddites and bad news for the paranoid. Hopefully, most people fall between those two opposites and with that, Silence on the Wire: A Field Guide to Passive Reconnaissance and Indirect Attacks is an fascinating book on knowing when to be suspicious and when to be complacent.

The premise of the book is that there are countless ways that a potential attacker can intercept information and sniff data. The title points out that these silent stealth-like attacks are often difficult to detect, and all the more so to defend against. The better you understand the threats, the better you can monitor and defend against them.

The author writes about his work with data reconnaissance and details how computers and networks operate, with a special emphasis on how they process and transmit data. With such transmissions, there are significant security threats; which is what this book details.

Make note that this is not a For Dummies type of book. It is written for security engineers and experienced system administrators that have a heavy background in networking and security. Electronic engineers will feel very much at home with the many schematics and encodings in the code. The book is written for those that are very comfortable with programming and complex networks.

The books 260 pages contain four parts and 18 chapters. Part one details the long journey that a keystroke takes. Between the keyboard and the ultimate destination of the data, there are myriad ways the data can be misappropriated. These include traditional attacks, in addition to protocol attacks and problems with the CPU.

Part 2 details how data is transmitted and the various avenues of attack that can be launched against the data. Note that the subtitle of the book is a field guide to passive reconnaissance and indirect attacks. The book is all about the passive types of attacks that are often quite prevalent, yet overlooked. In the section The Art of Transmitting Data, the author details the electronic mechanisms on how data traverses a network and the avenues of attacks. One of the easiest attacks is the monitoring of modem or router lights. With the proper analysis and deduction, an attacker can surmise a significant amount about the nature of the traffic.

Part 2 closes with an interesting overview of how to provide better security to switched Ethernet networks. The author notes that that Ethernet networks don't provide a universal and easy way to ensure the integrity and confidentiality (two pillars of security) of the data they transmit, or are they engineered to withstand malicious, intentionally injected traffic. Ethernet is simply a means for interfacing a number of local, presumably trusted systems. With such a premise, it is no wonder that security issues abound.

Part 3 spends about 100 pages on routing and security issues involved with TCP/IP. While there is not a significant amount of new information in these chapter (passive fingerprinting, fragmentation attacks, sequence number issues and more have been heavily documented), it provides a good overview of the inherent insecurity with the TCP/IP set of protocols.

Part 4 is closes with the authors notion of parasitic computing, which is when computations and storage in normal network traffic are hidden. With parasitic computing, data can be stored in mail queues and ICMP echoes, where remote hosts perform remote computations on them.

If you are looking for a book on quick tips to securing your network, Silence on the Wire: A Field Guide to Passive Reconnaissance and Indirect Attacks will not fill your need. This is a book written for those that want to know what goes on deep in the recesses of their computers, switches and network protocols. After reading the book, some may view it as an exercise in theoretical problems that bare little resemblance to the real world. But the fact is that many security problems that are originally labeled as theoretical and academic, end up being quite practical and devastating. Many software vendors will reply to a threat with a reply that it only applies to a lab scenario, only to quickly retreat and create a patch.

On the down side, the book can be dry at times. When you combine mathematical formulas, electronic engineering and abstract computer security, the book occasionally reads like James Joyce.

Overall, Silence on the Wire: A Field Guide to Passive Reconnaissance and Indirect Attacks is a most valuable book. It is a densely back whirlwind of deep technical information that gets to the very underpinning of computer security. Silence on the Wire makes you think about serious security problems that you never thought of before, or were even aware existed. Read it and get ready to be humbled.

I have an extensive library of computer security books, and this is by far the most interesting, most novel, most entertaining computer security book I own. I am actually going through each of the footnotes, reading every paper mentioned in the book. This books is not a textbook for system cracking or defending your system, like O'Reilly's Practical Unix and Internet Security (my second favorite security book). Instead Zalewski has gone somewhere entirely new, showing how your computer leaks information to other parties without 99.999% of the population realizing it. I do network security for a living, am a privacy fanatic, and figured I'd learn a few new things. I was overwhelmed by the amount of new information I learned. Reading this book was a humbling yet exhilirating experience. Some of the sections are written so clearly a lay person could understand them, but other sections assume a great deal of knowledge of computer lore, particularly TCP/IP networking. Buy this book, then run silent, run deep.

Excellent!

Zalewski's book is packed with information. The level of detail and technical difficulty of a lot of the information seem to make the book geared more toward those already familiar with computer security and information warfare rather than security novices. Those who are familiar with computer and network security may feel that parts of the book are too basic or beneath the level they are looking for, but Zalewski generally has a goal in mind and is just laying the groundwork to build up to it.

Most people in computer security, and even home users with little understanding of network security, are familiar with the major types of overt attacks (viruses, worms, phishing scams, spyware, etc.) and the countermeasures to protect their systems (antivirus, antispyware, firewalls, IDS, etc.), but this book uncovers the ominous volumes of data that can be extracted and exploited using passive reconnaissance techniques.

The book is called a "Field Guide" in the subtitle and it reads more or less like one. It provides the information and details you need in the trenches to wage an effective war against information insecurity. This is one that I would dub a "must read" for anyone working directly with network security.

[...]

At a conference I was at some time ago, a fellow mentioned to me that one person he would probably not want to play poker with is Michal Zalewski. I didn't really get his statement at the time, but after reading this book, I can now wholeheartedly understand his reluctance.

Although only 260 pages long, Michal's book covers an incredibly wide range of topics, pinpointing numerous areas in which incredible amounts of information about you and your computer are available, even though it may not seem that way at first blush. From the keyboard, to the processor, to the operating system, to the network wire, Michal points out the many holes from which this information is leaking from. His writing style gives rise to an entertaining narrative where a high-level picture makes the main concept available to everyone, while at the same time providing citations in the footnotes that let you delve into the details at a later point.

Silence on the Wire impressed me in so many ways that it's difficult to list them all here. Michal's understanding of so many areas in computer security is simply astounding. He covers each topic in just enough detail, not bogging down the reader in lots of technical jargon, but also not doing an inordinate amount of 'hand-waving'. His movement through the various components of the computer and the network is very well done; it ties together in a nice progression that the reader can follow easily.

I enjoyed the a nice selection of papers Michal discusses in which many ingenious attacks were described (timing attacks on RSA, SSH password recovery through timing analysis, TEMPEST, etc.). But one thing that truly stood out in this book is Michal's own contribution, which includes his work with p0f, the analysis of various ISN generators, and his work on identifying various web browsers through timing analysis. I was just amazed at how easily Michal pulled these 'fingerprints' out of seemingly random and/or innocuous data sets.

I had actually read about much of the work that Silence on the Wire covers beforehand, but in spite of that I learned a great deal from this book, and I know that many others can too. If you only read one book on network security, make it this one!

This is one of the few information security books that seem to age well: I reread it after over a year, and it still appears to be quite refreshing and up to date. This only goes to show the difference between books written out of genuine passion, and the rest. Big kudos to the author.

I thought this was an excellent break from the standard fare of titles on hacking. It brought to light the efforts people can take to gain information about your systems. While I'm very skilled in technology, some of the books out there can be quite detailed and boring. Silence did a great job of breaking things down to a clear and readable level, and still presented some very detailed items. Anyone interested in systems security should read this book as a baseline primer if nothing else.

First: this is ultra-heavy geek territory, but it's not necessarily computer geeks only. What I mean is that although this is all computer and networking related, any general engineering geek-type will probably enjoy it.

What I particularly liked is the author's attention to detail. I'd start reading a chapteer and think "Yeah, I know this", but then realize that he was just leading me through the basics because he had something important and interesting to say that I probably did NOT know.. and that was usually true.

And although there is a lot of ink devoted to explaining the background of things you may already know, I didn't mind it because the author has style and wit and presents things with a slant that makes it fun to read even when I already knew everything.

Before I was done with this, I cornered my geek son-in-law and had him read one chapter. He's very busy right now, and hasn't had time to read two other books I gave him last month. He read the chapter and I said "You want this when I'm done, right?". He said "Oh, yeah. Definitely".

Just when you thought you had a decent handle on how to protect yourself on-line, out comes a book that exposes a whole new series of exploits you probably haven't thought about... Silence on the Wire by Michal Zalewski.

Chapter List: I Can Hear You Typing; Extra Efforts Never Go Unnoticed; Ten Heads Of The Hydra; Working For The Common Good; Blinkenlights; Echoes Of The Past; Secure In Switched Networks; Us Versus Them; Foreign Accent; Advanced Sheep-Counting Strategies; In Recognition Of Anomalies; Stack Data Leaks; Smoke And Mirrors; Client Identification: Papers, Please!; The Benefits Of Being A Victim; Parasitic Computing, Or How Pennies Add Up; Topology Of The Network; Watching The Void; Closing Words; Bibliographic Notes; Index

The subtitle of this book is "a field guide to passive reconnaissance and indirect attacks", and that gives you a pretty good idea as to the direction that Zalewski is going with his information. While most security books deal with active attacks designed to either take over your system or crash it, Silence is more concerned with how you may be inadvertently giving up more information than you think. This may happen based on detailed analysis of the timing patterns on data sent over the network. By careful analysis, it's possible to deduce a significant percentage of the data, leaving the rest of the data vulnerable to statistical analysis and attack. Visual representation of IP sequence numbers can also give strong indications as to what type of system may be sending the packets. It could even be something as "innocent" as hi-tech monitoring of the blinking lights on the front of your modem. These types of attacks are not "script-kiddy" exploits, in that there is a lot of theory and analysis involved in interpreting the results. But the fact remains that someone you can't see may be getting more information about you than you think.

Zalewski goes into a lot of detail about the architectural underpinnings of a system in order to set the stage for the type of monitoring that can happen. If you're just looking for "how do I do a timing attack?", you'll probably go away very frustrated. But if you're the type of reader who asks "how does the design of a system facilitate that type of information leakage?", you'll definitely treasure this volume. The type of information that Zalewski covers here isn't readily available in any other single volume. Therefore, it fills a gap in the security library that most people don't even realize exists.

A good read that will open your eyes to problems you weren't even aware of...