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

Posted on by Ben Rothke

Silence on the Wire: a Field Guide to Passive Reconnaissance and Indirect Attacks is a deep and penetrating look at security. 

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 a 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.

Ben Rothke

Senior Information Security Manager, Tapad

data security

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