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Buffer Overflow Basics


A buffer overflow occurs when a program or process tries to store more data in a temporary data storage area than it was intended to hold. Since buffers are created to contain a finite amount of data, the extra information can overflow into adjacent buffers, corrupting or overwriting the valid data held in them.

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Open Source Tool of March: ZoneMinder


For January and February, we chose some of the staples of open source security (GnuPG and Nmap) as the tool of the month. And deservedly so; both have just celebrated their ten-year anniversary in the open source realm, a rare feat for any open source project, much less one founded on security.

But for the month of March, we wanted to move ahead and change gears. This month's Open Source Tool is no newbie for sure, but we bet that most of you reading haven't heard of it. While most Linux security tools deal with digital security, this month's tool is one of the few to cross that divide;

Welcome to Zone Minder, the Open Source Tool for March...

Open Source Tool of February: Nmap!


This February, the team at has chosen NMAP as the Open Source Security Tool of the Month!

In January, we chose GnuPG in part because it had just celebrated its 10th anniversary. Well, it wasn't alone. As of this past December Nmap ("Network Mapper"), the free and open source utility for network exploration and auditing, celebrated its 10th Anniversary as well! And because of its popularity, chances are very good that you've already used NMAP for quite some time. Even if you have, it's always good to take a look at how it all got started and what it's all about...

Master's Student: A Quick and Dirty Guide To Kernel Hardening with GrSecurity


Our resident Master's student Gian Spicuzza chimes in this month with a great feature HowTo on Kernel Hardening! There are a number of ways to lock down a system, and RBAC (role based access control) is one of them. Read on to learn more about what makes RBAC so useful, and to read one of the best overviews on Low/Medium/High Security...

The combination of the Linux kernel and GNU packages has always been regarded as a secure operating system, but can it be more secure? Kernel hardening is the answer to tightening up the Linux backbone. GrSecurity, a kernel patch for Linux, is one of the more popular approaches...

One of the most significant feature is the addition of a role-based access control system (RBAC) that monitors what each user can execute based on their role and denies execution if they overstep their pre-defined rules.

Knock, Knock, Knockin' on EnGarde's Door (with FWKNOP)


Secret knocks have been used for purposes as simple and childish as identifying friend or foe during a schoolyard fort war. Fraternities teach these knocks as a rite of passage into their society, and in our security world we can implement this layer of security to lock down an SSH server.
With this guide on FWKNOP by Eckie S. (one of our own), you are taken on an easy-to-follow process of securing your platform with your own client and server port knocking set-up.

Installation, iptable Rules setup, configuring access for the client and server, and everything in between.

Check it out!

IPTables HOWTO Updated Release


The aim of the iptables-tutorial is to explain iptables in a complete and simple way. The iptables-tutorial is currently rather stable, and contains information on all the currently available matches and targets (in kernel), as well as a couple of complete example scripts and explanations. It contains a complete section on iptables syntax, as well as other interesting commands such as iptables-save and iptables-restore. The tutorial has recently been under heavy scrutiny and updating, as can be seen in this, the latest version of the tutorial. It is now also available in bookform from If you feel like contributing or donating to the author of this tutorial, please do buy the book! Thank you!

Why EnGarde Secure Linux is "Secure By Design"


Secure By Design: How Guardian Digital Secures EnGarde Secure Linux


What is EnGarde Secure Linux?

EnGarde Secure Linux is not just another "repackaged" Linux distribution, but a modern open source system built from the ground up to provide secure services in the threatening world of the modern Internet. EnGarde Secure Linux is the creation of Guardian Digital, Inc. a pioneer in open source security since 1999, and has been developed since then in collaboration with the worldwide community of open source security enthusiasts and professionals. Guardian Digital provides a secure and consistent environment for EnGarde Secure Linux through the Guardian Digital WebTool and the Guardian Digital Secure Network. A server-only system, EnGarde Secure Linux is administered securely and remotely using the WebTool, a custom interface that both simplifies server administration and guides the system user in maintaining a secure configurations for all of the services that comprise EnGarde. The Guardian Digital Secure Network maintains the consistency and security of EnGarde by providing system upgrades and security patches that have been constructed by Guardian Digital's engineering team to relieve the user of the burden of maintaining the system in a consistent and secure state.

Defense In Depth In EnGarde Secure Linux

Security is the primary consideration in designing every element of EnGarde Secure Linux. Guardian Digital applies basic security principles like "least privilege", "no unnecessary services" and "default-deny" rules to every level of EnGarde from access to kernel itself to defense of the network perimeter. Security begins with the selection of the best available open source packages, chosen and tailored for maximum security and following software security best-practices. The next level of protection comes from a complete re-engineering of the standard Linux security model using Security Enhanced Linux (SELinux). SELinux implements the principle of "Mandatory Access Control" which places each program and process under the control of its own SELinux policy, limiting its access to files and resources and effectively containing any intrusions or compromises. EnGarde Secure Linux builds on this secure foundation by placing all administration of EnGarde and its services under the control of the Guardian Digital WebTool. The Guardian Digital WebTool is a secure, remote graphical administration interface that is carefully tailored, not just to simplify administration, but to help maintain secure practices and configurations. For example, EnGarde, through the WebTool, limits user and IP access by default for most services like FTP file transfers and POP/IMAP mail retrieval. For services that must be publicly accessible like Web service and mail transport, the WebTool offers simple setup of SSL-enabled encrypted services. The WebTool also mandates secure practices like encrypted passwords and prevents hazardous configurations like open mail relays. EnGarde Secure Linux extends its secure environment through the use of a carefully integrated selection of the best open source security tools for detecting compromises and intrusions at all levels. EnGarde generates special security-focused system logs to help the administrator identify potential compromises, and adds to this host-based intrusion detection tools. EnGarde monitors the system for potential network compromises and intrusions using the open source Snort intrusion detection system, adding its own NetDiff port status monitoring software.


Linux and open source systems have long been renowned for their stability, versatility and scalability. EnGarde Secure Linux adds the feature crucial to providing services on the modern Internet -- security. Guardian Digital builds security into every element of EnGarde by selecting the best available open source tools and services available and configuring them with security as the top priority. Recognizing that security can only be maintained in a consistent and stable environment, Guardian Digital relieves the user of the burden of "hardening" the system and following secure practices by designing secure administration into its WebTool and by updating and securing the system through the Guardian Digital Secure Network. For an in-depth exploration of the EnGarde Secure Linux security environment, see the full version of this document at "Secure By Design" full text

RFID with Bio-Smart Card in Linux


In this paper, we describe the integration of fingerprint template and RF smart card for clustered network, which is designed on Linux platform and Open source technology to obtain biometrics security. Combination of smart card and biometrics has achieved in two step authentication where smart card authentication is based on a Personal Identification Number (PIN) and the card holder is authenticated using the biometrics template stored in the smart card that is based on the fingerprint verification. The fingerprint verification has to be executed on central host server for security purposes. Protocol designed allows controlling entire parameters of smart security controller like PIN options, Reader delay, real-time clock, alarm option and cardholder access conditions.

The RF Smart Card and card reader/writer were developed to handle payment transaction for public transportation systems. These contact less cards have security features, such as encrypted RF transmission mutual authentication, and security keys. The RF smart card has up to 16 separate sectors, which can be configured as purses or for general data storage. The first sector is typically used as a directory for the rest of the card, leaving 15 segments available for data or purses.

Each sector has two keys, called the A and B keys, allowing different access privileges to that sector. These key pairs can be designated as read and read/write, or decrement and increment/decrement .For example this would allow turnstile readers with the A key to only deduct value from a card sector, while smart card readers with the B keys could either add or subtract value .The card also has a 32-bit unique random number, which is permanently encoded into each chip by the chip manufacturer. Public key infrastructure (PKI) based systems are used to construct a secure system that can achieve secure access conditions. They are consequently being used to carry keys and store personal information in applications such student identification systems.