Hacking Linux Exposed

I'm a big fan of the Hacking Exposed style of writing. All offensive theory is backed up by command line examples, followed by defensive countermeasures. Hacking Exposed: Linux, 2nd Ed (HE:L2E) follows this tradition, updating the content of the first edition and adding 200 pages of new content. Although I reviewed the first edition in Sep 01, reading the second edition reminded me of the challenges posed by securely configuring and deploying Linux systems. The best way to learn while reading HE:L2E is to try the sample commands. I also recommend visiting the links mentioned and installing many of the tools described by the authors. I found programs like raccess, nsat (ch. 3), sslsniff (ch. 7), nstx, and httptunnel (ch. 15) particularly interesting from an attacker's point of view. From a system administration standpoint, coverage of passlogd (ch. 2), lilo and grub (ch. 5), and X (ch. 6) were very helpful.The authors share many novel ways to abuse Linux systems, but counter those exploits with little-known features or third-party tools. I never knew I could use bash's HISTCONTROL feature to selectively remove entries from shell history files. HE:L2E goes the extra mile to help secure your system, such as including sample C code in ch. 13 to allow one to compile TCP Wrappers support into one's own programs. Other clear, concise defensive measures were introduced in excellent chapters on keeping the kernel and packages current (appendix B) and pro-active security measures (ch. 2). The last appendix gives a short yet powerful description of the damage an intruder can perform, showing how he hid unauthorized programs and how those programs were discovered. If you use Linux, you'll find HE:L2E indispensable. I even applied many of the tools and techniques to my FreeBSD system, showing that that good security advice can be a cross-platform endeavor.

Hacking Linux comes in six parts, each of which is worth the price of the book in whole. Part one: security overview covers all the basics like file permissions, setuserid problems, buffer overflows/format string attacks, tools to use before you go online, and mapping tools like nmap. Part two comes in from more of the hacker angle with social engineering and trojans, attacks from the console, and then concludes with two excellent chapters about netowrk attacks and TCP/IP vulnerabilities.All the stuff to this point assumes the hacker is on the outside. Part three takes over and shows you what the hacker will do once they've gotten on, such as attacking other local users including root, and cracking passwords. It becomes obvious that you need to protect things from insiders as much as from the outsider, because the outsider will usually get in as a normal user first, and if you can prevent him or her from getting root access, the damage cannot be nearly as severe. A lot of books don't cover this angle at all, and it's done superbly here.Part four covers common problems in internet services. First they discuss mail servers. Sendmail, Qmail, Postfix, and Exim each get covered in detail - it's nice to see more than just Sendmail discussed in a security book. Of course, it'd be even nicer to see something other than Sendmail installed on a Linux machine by default. Next they cover problems with FTP software and problems with the FTP protocol. I'd never seen "beneath the hood" and realized how wierd FTP really was, and why it's not supported by firewalls very well, and the authors show you the inner workings of it so anyone can understand the problems. They continue with Apache and CGI/mod_perl/PHP/etc problems, both from a coding standpoint and how to secure against outsiders and your own web developers. Next it's on to Firewalls (iptables and TCP wrappers) and lastly (distributed) denial of service attacks. The countermeasures for the DOS problems are excellent, and a must for anyone with a server. Part five covers everything a hacker can do once they've broken in. They describe trojan programs, trojan kernel modules, and configuration changes that can be used to keep root access, or hide the hacker activity, or let them get back in should the computer be partially fixed. This was not only complete, but scary in how many different things they showed. It works both as a blueprint for what you need to defend against, how to clean up after a hacker has gotten in, and also how you could back door a machine if you get in. I'll leave the ethics up to you. Lastly we have part six, which is the appendicies. While most times I ignore appendicies, these are really an integral part of the book, and are referenced throughout the book all over. (This very good, because it keeps the book from having too much repeated countermeasures.) They discuss post-breakin cleanup, updating your software and kernel, and turning off daemons (both local and ne

Hacking Linux Exposed by Brian Hatch, James Lee and George Kurtz, is a nice follow-up to their bestselling Hacking Exposed . While not as groundshaking as its predecessor, the new book does provide a good reference for people just starting with Linux. Anyone who is setting up or planning to set up a Linux network should consider owning it, together with the appropriate Linux administration manuals.Hacking Linux Exposed covers security administration issues such as FTP, sendmail (but for some reason, not POP3/IMAP servers) and web server setup; it also discusses local user security issues and touches lightly on Linux firewalling and other network access controls (TCP wrappers).The book includes a big section on keeping your system updated, which outlines methods used by several popular Linux distributions (rpm from RedHat, apt-get from Debian and pkgtool from Slackware). This information is essential to the security of any Linux machine, whether a home workstation or company server.The focus is Linux, but the book also covers some other important security areas. It attempts to offer a total solution for Linux security, starting with general infosec philosophy (such as proactive security), and moving on to physical security, social engineering, Trojan programs, access control, user security and server setup. Each security problem is rated for global risk on a 1 to 10 scale, factoring in frequency, simplicity and impact. In general, the book is more encyclopedia than detailed guide, as it strives toward breadth over depth.

I am a senior engineer for network security operations. I read "Hacking Linux Exposed" (HLE) to learn how adversaries compromise Linux hosts. HLE impressed me at every level. I highly recommend system administrators and security personnel read and heed this book's recommendations.The "Hacking Exposed" series is known for its unique example-driven style. Rather than telling the reader about a technique or problem, the authors demonstrate the issue using command-line examples. I find myself reading with book and laptop at hand, ready to duplicate the authors' sample commands. This process reinforces the authors' message, while the reader learns if a specific problem applies to his situation. Furthermore, by showing exactly how to execute certain commands, the authors impart bits of wisdom and trickery not found elsewhere.For example, chapter 11 describes attacks and defenses for FTP servers. To explain active and passive FTP sessions, the authors demonstrate running an FTP client with the -d switch to illustrate raw instructions sent by the client over the FTP command channel. I had never seen this switch in use, but as an intrusion detector I constantly see raw FTP instructions like those revealed by the -d switch. These and other tidbits, like using the chattr -i command or setting the "sticky bit", make HLE exceptional.Beyond these benefits, readers will enjoy clear, thorough explanations of Linux security issues. HLE gives first-rate descriptions of ssh and web man-in-the-middle attacks, race conditions, and FTP data hijacking. HLE also provides great illustrated examples of FTP bounce attacks, giving intrusion detectors the minutiae we need to recognize these techniques. I had heard of most of the compromise methods offered by HLE, but never seen them discussed in such practical detail.If the material in chapters 1-13 of HLE don't prompt you to verify your Linux host's integrity, then the case studies in appendix D will. The security community needs more of these narratives. These stories, based on true events, show the lengths to which some attacks will go to penetrate target machines."Hacking Linux Exposed" is another strong addition to the "Hacking Exposed" series, and the security community will benefit as a result.(Disclaimer: I received a free review copy from the publisher.)

I am in charge of network security for a large firm. We use largely FreeBSD and OpenBSD machines instead of Linux whenever possible. One of the junior folks was trying to convince us that Linux isn't all that bad, and pointed to this book as proof that it can be secured.Well, we're not about to switch. However this book covered so many unexpected issues that affected our *BSD boxen that we spent a solid week implementing changes on all our systems. The detail of this book was superb, and it was easy to figure out the differences between their Linux-specific solutions and what was needed on our *BSD systems when they weren't exactly the same.Got Unix? Buy this book.