Cybersecurity: Crash Course Computer Science #31

Summary

In this CrashCourse Computer Science episode, Carrie Anne explores the importance of cybersecurity, emphasizing the need to protect computer systems and data from threats. She explains the three main goals of cybersecurity: secrecy, integrity, and availability, and how they are compromised through data breaches, unauthorized modifications, and denial of service attacks. The video delves into threat modeling, authentication methods (what you know, what you have, and what you are), and the significance of access control through permissions and models like Bell-LaPadula. Carrie Anne also touches on the challenges of ensuring software security and the strategies to mitigate risks, including code auditing, isolation, and sandboxing.

Takeaways

• 🌐 Cybersecurity is crucial for protecting computer systems and data from unauthorized access and malicious activities, just as physical security measures protect our real-world assets.
• 🔐 The three main goals of cybersecurity are to ensure the secrecy (confidentiality), integrity, and availability of computer systems and data.
• 👤 Authentication is the process of verifying the identity of users, and it can be based on 'what you know' (like passwords), 'what you have' (like keys or tokens), or 'what you are' (biometrics).
• 🔑 'What you know' authentication is vulnerable to brute force attacks where hackers use automated systems to guess passwords or PINs.
• 🛡️ Longer and more complex passwords, or using passphrases, significantly increase the difficulty for attackers to crack them through brute force.
• 🔗 'What you have' authentication relies on physical possession, which is harder for remote attackers to compromise but can be copied or stolen if the attacker is physically close.
• 👁️‍🗨️ 'What you are' authentication uses biometrics, which can be very secure but also has issues with accuracy and the permanent nature of biometric data.
• 🔐 Two-factor or multi-factor authentication combines multiple forms of authentication to provide stronger security by making it harder for attackers to compromise multiple factors.
• 📋 Access Control Lists (ACLs) define who can read, write, or execute files, folders, and programs, ensuring that users only have access appropriate to their clearance level.
• 🛠️ The Bell-LaPadula model is an access control model that prevents 'read up' and 'write down' privileges to maintain secrecy and prevent accidental information leaks.
• 🏭 Isolation techniques like sandboxing applications or using virtual machines limit the damage from a compromised program by containing it within a separate environment.

Q & A

What is the primary purpose of cybersecurity?

The primary purpose of cybersecurity is to minimize crime and harm in the virtual world, similar to how physical security measures like locks, fences, and police officers minimize crime in the real world.

What are the three main goals of cybersecurity?

The three main goals of cybersecurity are to protect the secrecy (confidentiality), integrity, and availability of computer systems and data against threats.

What is a threat model in the context of cybersecurity?

A threat model is a specification that profiles potential attackers, including their capabilities, goals, and probable means of attack, known as an attack vector. It helps security experts prepare against specific threats rather than being overwhelmed by all possible attack methods.

Why is it important to differentiate between 'what you know', 'what you have', and 'what you are' authentication methods?

Differentiating between these authentication methods is important because each has its own strengths and weaknesses. 'What you know' relies on knowledge of a secret, 'what you have' on possession of a token, and 'what you are' on biometric data. Understanding these differences helps in choosing the most appropriate method for a given security scenario.

How does a brute force attack work?

A brute force attack works by systematically trying every possible combination of a password or PIN until the correct one is found. It is a trial-and-error method that relies on computational power rather than clever algorithms.

What is the significance of using complex passwords with a mix of characters?

Using complex passwords with a mix of upper and lowercase letters, special symbols, and numbers significantly increases the number of possible combinations, making it much harder for attackers to guess or crack the password through methods like brute force attacks.

Why is two-factor or multi-factor authentication recommended for important accounts?

Two-factor or multi-factor authentication is recommended because it adds an additional layer of security. Even if an attacker guesses your password or steals your authentication token, it is much harder for them to compromise both factors, providing stronger protection for important accounts.

What is the Bell-LaPadula model and how does it relate to access control?

The Bell-LaPadula model is an access control model that enforces the principles of 'no read up' and 'no write down'. It ensures that users with lower clearance levels cannot access higher classified information and that users with higher clearance cannot inadvertently leak information by writing it to lower classified files.

How can the principle of isolation help in computer security?

The principle of isolation in computer security helps by containing the damage caused by a compromised program. By sandboxing applications or running them in separate virtual machines, if one program is compromised, it is less likely to affect other programs or the overall system.

What is the role of independent verification and validation in ensuring software security?

Independent verification and validation play a crucial role in software security by having code audited by a crowd of security-minded developers. This process helps identify and fix vulnerabilities that the original developers might have missed, thus enhancing the security of the software.

Outlines

00:00

🔒 Introduction to Cybersecurity

Carrie Anne introduces the topic of cybersecurity, emphasizing the importance of protecting computer systems and data from threats, similar to how physical security is maintained in the real world. Cybersecurity aims to ensure the confidentiality, integrity, and availability of information. The paragraph discusses the three main goals of cybersecurity: secrecy (confidentiality), integrity, and availability. It also introduces the concept of a threat model, which is a framework for understanding potential attackers and their capabilities, helping to prepare defenses against specific threats. The analogy of securing a laptop against different threat models, such as a nosy roommate versus a mischievous sibling, illustrates how security measures are tailored to the perceived threat.

05:00

🔑 Authentication Methods in Cybersecurity

This section delves into the various methods of authentication used to verify the identity of users. The three primary types are 'What you know' (e.g., passwords), 'What you have' (e.g., security tokens), and 'What you are' (e.g., biometrics). Each method has its pros and cons. For instance, passwords are susceptible to guessing or brute force attacks, while physical tokens can be stolen or lost. Biometric authentication, although seemingly secure, faces challenges like the inability to reset compromised data and the potential for false positives or negatives. The paragraph highlights the importance of using complex passwords and the concept of two-factor or multi-factor authentication to enhance security. It also touches on access control, which involves defining permissions and access control lists to regulate what authenticated users can do within a system.

10:02

🛡 Advanced Security Measures and Future Topics

The final paragraph discusses advanced security measures such as minimizing code to reduce the chance of implementation errors, the concept of a 'security kernel' or 'trusted computing base', and the practice of Independent Verification and Validation (IV&V) to audit code for security. It also mentions the DEF CON conference as a place where security experts share knowledge. The principle of isolation is introduced to limit the damage when a system is compromised, with techniques like sandboxing applications or running virtual machines. The paragraph concludes with a teaser for upcoming episodes, which will cover network security, hacker methods, and encryption, and ends with practical advice for viewers on password strength, two-factor authentication, and email safety.

Keywords

💡Cybersecurity

Cybersecurity refers to the practice of protecting computer systems, networks, and data from digital attacks. It is a critical component in the digital age, ensuring the confidentiality, integrity, and availability of information. In the script, cybersecurity is likened to the Jedi Order, emphasizing its role in maintaining peace and justice in the cyber-verse. The video discusses various aspects of cybersecurity, including threat models and access control, to illustrate its importance in safeguarding against cyber threats.

💡Threat Model

A threat model is a conceptual framework used to identify and understand potential adversaries and their attack vectors. It helps in profiling attackers' capabilities, goals, and probable means of attack. In the context of the video, a threat model is used to prepare against specific threats rather than being overwhelmed by all possible attack scenarios. The script uses the example of a nosy roommate to illustrate how threat models can guide security measures, such as hiding a laptop in a dirty laundry hamper to preserve its secrecy, integrity, and availability.

💡Authentication

Authentication is the process of verifying the identity of a user or device accessing a system. It is fundamental to cybersecurity as it determines who has the right to access certain resources. The video outlines three types of authentication: 'what you know' (e.g., passwords), 'what you have' (e.g., security tokens), and 'what you are' (e.g., biometrics). Each method has its pros and cons, and the script emphasizes the importance of using a combination of these methods for stronger security, known as two-factor or multi-factor authentication.

💡Access Control

Access control is the selective restriction of access to a system or network based on the identity of the user or device. It is a crucial aspect of cybersecurity that ensures only authorized individuals can access certain resources. The video discusses how access control is implemented through permissions or access control lists (ACLs), which define what each user can do with files, folders, and programs. The script also mentions the 'Bell-LaPadula model' as an example of a formalized approach to access control, which prevents unauthorized access to sensitive information.

💡Confidentiality

Confidentiality, also known as secrecy, is one of the three core goals of cybersecurity. It ensures that sensitive information is only accessible to authorized individuals. The script uses the example of data breaches, where hackers reveal credit card information, to illustrate an attack on confidentiality. Maintaining confidentiality is essential to protect privacy and prevent unauthorized disclosure of information.

💡Integrity

Integrity in cybersecurity refers to the assurance that data or a system has not been tampered with or altered in an unauthorized manner. It ensures that only authorized users can modify systems and data. The video provides the example of hackers using stolen passwords to send emails while impersonating someone else, which is an integrity attack. Upholding integrity is vital for maintaining the accuracy and reliability of information.

💡Availability

Availability ensures that authorized users have consistent and uninterrupted access to information and resources. Denial of Service (DoS) attacks, where hackers overload a website with fake requests to make it slow or unreachable, are direct attacks on availability. The video emphasizes the importance of availability in ensuring that systems and data remain accessible and functional for legitimate users.

💡Brute Force Attack

A brute force attack is a trial-and-error method used to obtain information such as a password by systematically trying every possible combination. The script mentions how computers can quickly attempt all possible combinations of a 4-digit PIN, making it an example of a brute force attack. This method is simple but effective, and it underscores the importance of using complex passwords or PINs to enhance security.

💡Malware

Malware, short for malicious software, is any software intentionally designed to cause harm to a computer, server, client, or computer network. In the video, malware is mentioned as a type of software that can compromise the security of a system by providing attackers with a backdoor. The script highlights the importance of ensuring that the hardware and software running security programs are free from malware to maintain the integrity of the security measures.

💡Isolation

Isolation in the context of cybersecurity refers to the practice of separating and protecting parts of a system to minimize the impact of a security breach. The video discusses 'sandboxing' as a method of isolation, where applications are contained in a restricted environment, preventing them from affecting other parts of the system. This approach is crucial for limiting the damage when an attacker compromises a program or system.

💡Virtual Machines

A virtual machine (VM) is a software emulation of a computer system. In the video, virtual machines are mentioned as a tool for achieving isolation. By running multiple VMs, each with its own sandbox, a single compromised VM can be contained, preventing the spread of an attack to other VMs. This concept is integral to the video's discussion on containment strategies for enhancing system security.

Highlights

Cybersecurity is crucial for minimizing crime and harm in the virtual world, similar to physical security measures in the real world.

Computers lack ethics and can be used for both beneficial and malicious purposes.

Cybersecurity aims to protect the secrecy, integrity, and availability of computer systems and data.

Secrecy ensures only authorized access to systems and data, like preventing data breaches.

Integrity ensures only authorized users can modify systems and data, preventing impersonation attacks.

Availability ensures continuous access to systems and data, countering Denial of Service Attacks.

A threat model profiles potential attackers to prepare against specific threats.

Physical security measures can be adapted to digital contexts, like hiding a laptop in a dirty laundry hamper.

Authentication methods include 'what you know', 'what you have', and 'what you are', each with pros and cons.

Brute force attacks attempt all possible combinations to gain unauthorized access.

Longer and more complex passwords significantly increase the difficulty for attackers.

Biometric authentication, like fingerprint readers, offers high security but has its own set of challenges.

Two-factor or multi-factor authentication combines multiple forms of authentication for increased security.

Access Control Lists (ACL) define permissions for users to ensure they only access appropriate resources.

The Bell-LaPadula model prevents 'read up' and 'write down' to maintain information secrecy and integrity.

Security kernels or trusted computing bases aim to minimize code and reduce implementation errors.

Independent Verification and Validation involves auditing code by external developers to find and fix bugs.

Isolation techniques, like sandboxing, limit the damage when a program is compromised.

Virtual Machines provide isolated environments to contain potential security breaches.

Cybersecurity is an ongoing challenge that requires constant vigilance and adaptation to new threats.

Transcripts

Hi, I’m Carrie Anne, and welcome to CrashCourse Computer Science!

Over the last three episodes, we’ve talked about how computers have become interconnected,

allowing us to communicate near-instantly across the globe.

But, not everyone who uses these networks is going to play by the rules, or have our

best interests at heart.

Just as how we have physical security like locks, fences and police officers to minimize

crime in the real world, we need cybersecurity to minimize crime and harm in the virtual

world.

Computers don’t have ethics.

Give them a formally specified problem and they’ll happily pump out an answer at lightning

speed.

Running code that takes down a hospital’s computer systems until a ransom is paid is

no different to a computer than code that keeps a patient's heart beating.

Like the Force, computers can be pulled to the light side or the dark side.

Cybersecurity is like the Jedi Order, trying to bring peace and justice to the cyber-verse.

INTRO

The scope of cybersecurity evolves as fast as the capabilities of computing, but we can

think of it as a set of techniques to protect the secrecy, integrity and availability of

computer systems and data against threats.

Let’s unpack those three goals:

Secrecy, or confidentiality, means that only authorized people should be able to access

or read specific computer systems and data.

Data breaches, where hackers reveal people’s credit card information, is an attack on secrecy.

Integrity means that only authorized people should have the ability to use or modify systems

and data.

Hackers who learn your password and send e-mails masquerading as you, is an integrity attack.

And availability means that authorized people should always have access to their systems

and data.

Think of Denial of Service Attacks, where hackers overload a website with fake requests

to make it slow or unreachable for others.

That’s attacking the service’s availability.

To achieve these three general goals, security experts start with a specification of who

your “enemy” is, at an abstract level, called a threat model.

This profiles attackers: their capabilities, goals, and probable means of attack – what’s

called, awesomely enough, an attack vector.

Threat models let you prepare against specific threats, rather than being overwhelmed by

all the ways hackers could get to your systems and data.

And there are many, many ways.

Let’s say you want to “secure” physical access to your laptop.

Your threat model is a nosy roommate.

To preserve the secrecy, integrity and availability of your laptop, you could keep it hidden in

your dirty laundry hamper.

But, if your threat model is a mischievous younger sibling who knows your hiding spots,

then you’ll need to do more: maybe lock it in a safe.

In other words, how a system is secured depends heavily on who it’s being secured against.

Of course, threat models are typically a bit more formally defined than just “nosy roommate”.

Often you’ll see threat models specified in terms of technical capabilities.

For example, “someone who has physical access to your laptop along with unlimited time”.

With a given threat model, security architects need to come up with a solution that keeps

a system secure – as long as certain assumptions are met, like no one reveals their password

to the attacker.

There are many methods for protecting computer systems, networks and data.

A lot of security boils down to two questions: who are you, and what should you have access to?

Clearly, access should be given to the right people, but refused to the wrong people.

Like, bank employees should be able to open ATMs to restock them, but not me… because

I’d take it all... all of it!

That ceramic cat collection doesn’t buy itself!

So, to differentiate between right and wrong people, we use authentication - the process

by which a computer understands who it’s interacting with.

Generally, there are three types, each with their own pros and cons:

What you know.

What you have.

And what you are.

What you know authentication is based on knowledge of a secret that should be known only by the

real user and the computer, for example, a username and password.

This is the most widely used today because it’s the easiest to implement.

But, it can be compromised if hackers guess or otherwise come to know your secret.

Some passwords are easy for humans to figure out, like 12356 or q-w-e-r-t-y.

But, there are also ones that are easy for computers.

Consider the PIN: 2580.

This seems pretty difficult to guess – and it is – for a human.

But there are only ten thousand possible combinations of 4-digit PINs.

A computer can try entering 0000, then try 0001, and then 0002, all the way up to 9999...

in a fraction of a second.

This is called a brute force attack, because it just tries everything.

There’s nothing clever to the algorithm.

Some computer systems lock you out, or have you wait a little, after say three wrong attempts.

That’s a common and reasonable strategy, and it does make it harder for less sophisticated

attackers.

But think about what happens if hackers have already taken over tens of thousands of computers,

forming a botnet.

Using all these computers, the same pin – 2580 – can be tried on many tens of thousands

of bank accounts simultaneously.

Even with just a single attempt per account, they’ll very likely get into one or more

that just happen to use that PIN.

In fact, we’ve probably guessed the pin of someone watching this video!

Increasing the length of PINs and passwords can help, but even 8 digit PINs are pretty

easily cracked.

This is why so many websites now require you to use a mix of upper and lowercase letters,

special symbols, and so on – it explodes the number of possible password combinations.

An 8-digit numerical PIN only has a hundred million combinations – computers eat that

for breakfast!

But an 8-character password with all those funky things mixed in has more than 600 trillion

combinations.

Of course, these passwords are hard for us mere humans to remember, so a better approach

is for websites to let us pick something more memorable, like three words joined together:

“green brothers rock” or “pizza tasty yum”.

English has around 100,000 words in use, so putting three together would give you roughly

1 quadrillion possible passwords. Good luck trying to guess that!

I should also note here that using non-dictionary words is even better against more sophisticated

kinds of attacks, but we don’t have time to get into that here.

Computerphile has a great video on choosing a password - link in the dooblydoo.

What you have authentication, on the other hand, is based on possession of a secret token

that only the real user has.

An example is a physical key and lock.

You can only unlock the door if you have the key.

This escapes this problem of being “guessable”.

And they typically require physical presence, so it’s much harder for remote attackers

to gain access.

Someone in another country can’t gain access to your front door in Florida without getting

to Florida first.

But, what you have authentication can be compromised if an attacker is physically close.

Keys can be copied, smartphones stolen, and locks picked.

Finally, what you are authentication is based on... you!

You authenticate by presenting yourself to the computer.

Biometric authenticators, like fingerprint readers and iris scanners are classic examples.

These can be very secure, but the best technologies are still quite expensive.

Furthermore, data from sensors varies over time.

What you know and what you have authentication have the nice property of being deterministic

– either correct or incorrect.

If you know the secret, or have the key, you’re granted access 100% of the time.

If you don’t, you get access zero percent of the time.

Biometric authentication, however, is probabilistic.There’s some chance the system won’t recognize you…

maybe you’re wearing a hat or the lighting is bad.

Worse, there’s some chance the system will recognize the wrong person as you – like

your evil twin!

Of course, in production systems, these chances are low, but not zero.

Another issue with biometric authentication is it can’t be reset.

You only have so many fingers, so what happens if an attacker compromises your fingerprint data?

This could be a big problem for life.

And, recently, researchers showed it’s possible to forge your iris just by capturing a photo

of you, so that’s not promising either.

Basically, all forms of authentication have strengths and weaknesses, and all can be compromised

in one way or another.

So, security experts suggest using two or more forms of authentication for important

accounts.

This is known as two-factor or multi-factor authentication.

An attacker may be able to guess your password or steal your phone: but it’s much harder

to do both.

After authentication comes Access Control.

Once a system knows who you are, it needs to know what you should be able to access,

and for that there’s a specification of who should be able to see, modify and use what.

This is done through Permissions or Access Control Lists (ACL), which describe what access

each user has for every file, folder and program on a computer.

“Read” permission allows a user to see the contents of a file, “write” permission

allows a user to modify the contents, and “execute” permission allows a user to

run a file, like a program.

For organizations with users at different levels of access privilege – like a spy

agency – it’s especially important for Access Control Lists to be configured correctly

to ensure secrecy, integrity and availability.

Let’s say we have three levels of access: public, secret and top secret.

The first general rule of thumb is that people shouldn’t be able to “read up”.

If a user is only cleared to read secret files, they shouldn’t be able to read top secret

files, but should be able to access secret and public ones.

The second general rule of thumb is that people shouldn’t be able to “write down”.

If a member has top secret clearance, then they should be able to write or modify top

secret files, but not secret or public files.

It may seem weird that even with the highest clearance, you can’t modify less secret files.

But, it guarantees that there’s no accidental leakage of top secret information into secret

or public files.

This “no read up, no write down” approach is called the Bell-LaPadula model.

It was formulated for the U.S. Department of Defense’s Multi-Level Security policy.

There are many other models for access control – like the Chinese Wall model and Biba model.

Which model is best depends on your use-case.

Authentication and access control help a computer determine who you are and what you should

access, but depend on being able to trust the hardware and software that run the authentication

and access control programs.

That’s a big dependence.

If an attacker installs malicious software – called malware – compromising the host

computer’s operating system, how can we be sure security programs don’t have a backdoor

that let attackers in?

The short answer is… we can’t.

We still have no way to guarantee the security of a program or computing system.

That’s because even while security software might be “secure” in theory, implementation

bugs can still result in vulnerabilities.

But, we do have techniques to reduce the likelihood of bugs, quickly find and patch bugs when

they do occur, and mitigate damage when a program is compromised.

Most security errors come from implementation error.

To reduce implementation error, reduce implementation.

One of the holy grails of system level security is a “security kernel” or a “trusted

computing base”: a minimal set of operating system software that’s close to provably secure.

A challenge in constructing these security kernels is deciding what should go into it.

Remember, the less code, the better!

Even after minimizing code bloat, it would be great to “guarantee” that code as written

is secure.

Formally verifying the security of code is an active area of research.

The best we have right now is a process called Independent Verification and Validation.

This works by having code audited by a crowd of security-minded developers.

This is why security code is almost always open-sourced.

It’s often difficult for people who wrote the original code to find bugs, but external

developers, with fresh eyes and different expertise, can spot problems.

There are also conferences where like-minded hackers and security experts can mingle and

share ideas, the biggest of which is DEF CON, held annually in Las Vegas.

Finally, even after reducing code and auditing it, clever attackers are bound to find tricks

that let them in.

With this in mind, good developers should take the approach that, not if, but when their

programs are compromised, the damage should be limited and contained, and not let it compromise

other things running on the computer.

This principle is called isolation.

To achieve isolation, we can “sandbox” applications.

This is like placing an angry kid in a sandbox; when the kid goes ballistic, they only destroy

the sandcastle in their own box, but other kids in the playground continue having fun.

Operating Systems attempt to sandbox applications by giving each their own block of memory that

others programs can’t touch.

It’s also possible for a single computer to run multiple Virtual Machines, essentially

simulated computers, that each live in their own sandbox.

If a program goes awry, worst case is that it crashes or compromises only the virtual

machine on which it’s running.

All other Virtual Machines running on the computer are isolated and unaffected.

Ok, that’s a broad overview of some key computer security topics.

And I didn’t even get to network security, like firewalls.

Next episode, we’ll discuss some specific example methods hackers use to get into computer

systems.

After that, we’ll touch on encryption.

Until then, make your passwords stronger, turn on 2-factor authentication, and NEVER

click links in unsolicited emails!

I’ll see you next week.