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Showing 215 results for the search term "John McDermott".


How to Test File Permissions with Bash  

Recently, I posted about basic permissions for Linux files; now let’s look at how to access those in a shell script. Testing file permissions is an essential part of enforcing an access control policy. Two common ways to test files for readability, writability, zero size and so forth are the if and the test. For […]



How to Verify Windows File Integrity with Hashes

As I write this, I am developing a skill (app) for Amazon’s Alexa voice service. A couple of days into the development I thought I’d accidently corrupted a critical file. Fortunately, I hadn’t, but it reminded me of the practice of discovering file changes by comparing file hash values against a baseline. The basic idea […]



Unleashing Wireshark’s Powerful Follow TCP Stream Feature

In security courses such as Learning Tree’s System and Network Security Introduction, we often hear about the insecurity of protocols such as Telnet. These older protocols send their data – including login credentials – over the network in the clear. While ssh, a secure alternative to Telnet, is used in many applications today, many sites […]



A New Way To Learn the Critical Skill of Storytelling

A critical skill for leaders and aspiring leaders is storytelling. Throughout history, stories have been an essential form of communication. Brain science even gives us reasons why. I love to listen to and tell stories. Most people do. We tell stories to friends at social gatherings, share stories about work successes and failures, tell stories […]



Introduction to UNIX-family File Permissions

Learning Tree’s System and Network Security Introduction course begins with a description of the four fundamental concepts of cyber security: authentication, confidentiality, integrity, and availability. That leads into a discussion of authorization: “who is allowed to do what.” The conclusion is the “access equation”: Authentication + Authorization = Access (We also discuss situations where access is […]


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