Linux Security Fundamentals

David Clinton

• Publisher: Sybex
• Year: 2020
• ISBN:
  9781119781561
• Edition: 1
• Topic: Computer Science
• Subtopic: Operating Systems
• Index: Computer Science

Linux Security Fundamentals provides basic foundational concepts of securing a Linux environment. The focus is the digital self-defense of an individual user. This includes a general understanding of major threats against individual computing systems, networks, services and identity as well as approaches to prevent and mitigate them. This book is useful for anyone considering a career as a Linux administrator or for those administrators who need to learn more about Linux security issues. Topics include:

• Security Concepts
• Encryption
• Node, Device and Storage Security
• Network and Service Security
• Identity and Privacy

Readers will also have access to Sybex's superior online interactive learning environment and test bank, including chapter tests, a practice exam, electronic flashcards, a glossary of key terms.

Chapter 1
Using Digital Resources Responsibly

“With great power comes great responsibility.”

Words of wisdom. That’s the message displayed for administrators when they log in for the first time to many Linux distributions. Who said those words first? Aristotle? Kant? Nope. Spider-Man’s uncle. But hey, accept the truth from any source.

While we’ll discuss protecting yourself from attack at length later in the book, this chapter is all about responsibilities. It’s about your responsibilities both as a consumer of computer technologies and as an administrator of computer technologies. It’s your job to make sure nothing you do online or with your devices causes harm to anyone’s assets.

How is all this relevant to the world of information technology (IT) and, specifically, to IT security? Computers amplify your strengths. No matter how much you can remember, how fast you can calculate, or how many people’s lives you can touch, it’ll never come close to the scope of what you can do with a computing device and a network. So, given the power inherent in digital technologies and the depth of chaos such power can unleash, you need to understand how it can all go wrong before you set off to use it for good.

The rest of this chapter will explore the importance of considering how your actions can impact people’s personal and property rights and privacy and how you can both ensure and assess the authenticity of online information.

I’m not a lawyer and this book doesn’t pretend to offer legal advice, so we’re not going to discuss some of the more esoteric places where individual rights can come into conflict with events driven by technology. Instead we’ll keep it simple. People should be able to go about their business and enjoy their interactions with each other without having to worry about having physical, financial, or emotional injury imposed on them. And you should be ready to do whatever is necessary to avoid or prevent such injuries.

Protecting Personal Rights

These days, the greatest technology-based threats to an individual’s personal well-being will probably exist on one or another social media platform. Facebook, Twitter, LinkedIn, and other online sites present opportunities for anyone to reach out to and communicate with millions or even billions of other users. This can make it possible to build entire businesses or social advocacy movements in ways that would have been unthinkable just a few years back. But, as we all now know, it also makes it possible to spread dangerous scams, political mischief, and social conflict.

As the man said, “With great power comes great responsibility.” Therefore, you need to be conscious of the possible impact of any interaction you undertake. This will be true not only for your use of your own social media or email/messaging accounts but also for any interactions taking place on sites or platforms you administrate. You could, for instance, be held legally responsible for anonymous comments left on your blog or for the use of email accounts belonging to your organization. It can be a hard balance to achieve. Are your policies unnecessarily allowing damaging content to be published or, alternatively, unfairly restricting innocuous content?

A helpful tool for maintaining perspective in these areas is to apply the grandmother test. What’s that? Before posting a message or comment on any online forum, take a minute to read it over one or two more times and then ask yourself, “Would both my grandmothers approve of what I’ve written? Is there anything that would make them uncomfortable?” In other words, ask yourself whether anyone could reasonably feel threatened or bullied by what you’re about to publish. The bottom line is to make generous use of common sense and goodwill.

With typical attention to such details, the social media community has come up with new names to describe each of the nastiest online threats. You should, unfortunately, be familiar with each of them.

Cyberstalking Stalking isn’t specific to online activities, but that doesn’t make it any less frightening. In general terms, a stalker persistently follows and observes a target, often with the goal of forcing an unwanted reaction. In the online world, cyberstalking can include electronic monitoring of a target’s online accounts and activities. Harassing cyberstalking can escalate beyond mere monitoring to include threats, slander, and identity theft.

Cybermobbing Mobbing involves large groups of people banding together to engage in bullying behavior. The nature of many social networking platforms—in particular the prevalence of anonymous accounts and the ease by which users can connect to each other—lends itself to mob formation. Often, all it can take is a single public post expressing an unpopular position and the power of tens of thousands of users can be brought to bear with the goal of making life miserable for the post’s author.

Doxxing Whether you present yourself to the online world using your real name or through an anonymous identity, you certainly don’t want your complete personal profile to become public. Considering all the data that’s already available on the internet, it’s often not hard for people with time on their hands to track down your physical address and private phone numbers. But making such information easily available on popular social media sites with the intention of causing the target harm is wrong—and, in some jurisdictions, also a crime. Victims of public doxxing have experienced relatively mild annoyances like middle-of-the-night pizza deliveries. But the practice has also proven deadly: it’s been used as part of “swatting” attacks, where people call a victim’s local police department claiming there’s a violent crime in progress at the victim’s address. More than one doxxer has been imprisoned for what must have seemed like a clever prank.

Protecting Digital Privacy

Your primary concern must always be to secure the data under your control. But have you ever wondered why that is? What’s the worst that could happen if copies of your data are stolen. After all, you’ll still have the originals, right? Well, if your organization is in the business of profiting from innovations and complex, hard-to-reproduce technology stacks, then the consequences of data theft are obvious. But even if your data contains nothing more than private and personal information, there’s a lot that can go wrong.

Let’s explore all that by way of posing a few questions.

What Is Personal Data?

Your personal data is any information that relates to your health, employment, banking activities, close relationships, and interactions with government agencies. In most cases, you should have the legal right to expect that such information remains inaccessible to anyone without your permission.

But “personal data” could also be anything that you contributed with the reasonable expectation that it would remain private. That could include exchanges of emails and messages or recordings and transcripts of phone conversations. It should also include data—like your browser search history—saved to the storage devices used by your compute devices.

Governments, citing national interest concerns, will reserve the right for their security and enforcement agencies to forcibly access your personal data where legally required. Of course, different governments will set the circumstances defining “legally required” according to their own standards. When you disagree, some jurisdictions permit legal appeal.

Where Might My Personal Data Be Hanging Out?

The short answer to that question is “Probably a whole lot of places you wouldn’t approve.” The long answer will begin with something like “I can tell you, but expect to become and remain deeply stressed and anxious.” In other words, it won’t be pretty. But since you asked, here are some things to consider.

Browsing Histories

The digital history of the sites you’ve visited on your browser can take more than one form. Your browser can maintain its own log of the URLs of all the pages you’ve opened. Your browser’s cache will hold some of the actual page elements (like graphic images) and state information from those web...