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Vulnerability Classification: Zero Day and Others Explained

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7 min read
published on March 18, 2025
updated on June 07, 2025

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Vulnerability Classification: Zero Day and Others Explained

Let's imagine two friends named Alice and Bob. Alice is using her favorite computer, and Bob is a curious person who sometimes tries to see if he can peek into Alice's computer. Vulnerabilities (vulnerability is commonly used word for 'weaknesses' by cybersecurity professionals) are basically little cracks or holes in the computer's wall that Bob could use to sneak in. We classify these cracks in different ways so we know how big or scary they are. Let's look at them together.

flowchart TD A[Alice's Computer] --> B[Security Wall] B --> C{Vulnerabilities} C --> D[Small Cracks] C --> E[Hidden Holes] C --> F[Weak Points] G[Bob] --> |Tries to Exploit| C

What Is a Zero Day Vulnerability?

A zero day vulnerability is a secret crack that nobody knew about, not even the good guys who built the software! When bad guys find that crack first, they can sneak in before anyone else can fix it. It is called zero day because we have zero days to fix it once it becomes known. That's like having a surprise hole in the wall that you only notice when the wind blows through, it's new and nobody prepared for it.

flowchart TD A[Software Released] --> B[Unknown Hole aka Zero Day Vulnerability] B --> C[Bad Guys Find It First] C --> D[Attack Happens Immediately] D --> E[No Time to Fix]

When Bob finds a zero day, he can get in before Alice even knows there's a problem. So it's super important to have good security teams checking for surprises to fix them as quickly as possible.

Other Types of Vulnerabilities

1. Known But Unpatched Vulnerabilities

This is when we already know about the hole, but haven't covered it up yet. For example, imagine Alice found a small crack in her house window. She knows it's there but hasn't gotten any tape or glue to fix it. If Bob learns about that crack, he might be able to slip a note through or even open it more. In software, we fix it by installing something called a patch, which is basically like a sticker to cover the hole.

flowchart TD X[Crack Detected] --> Y[Patch Available] Y --> Z[Users Not Applying Patch = Risk]

2. Misconfiguration Vulnerabilities

Let's say Alice has a big fence around her backyard but forgets to lock the gate. The fence looks safe from afar, but the open gate means Bob can walk right in. That is a misconfiguration. In computers, it means leaving default passwords or forgetting to set the right security settings. It's simple to fix, but often people forget.

3. Injection Vulnerabilities (Like SQL Injection)

Imagine if Alice wrote a list of her secrets on a piece of paper. Bob sneaks an extra note in that list to trick her. That is an "injection." In computer talk, Bob might sneak in special code or instructions into a website or database to make it do something it should not do, like share personal info. It's basically tricking the system by adding surprise notes that break the rules.

flowchart TD A1[Web Shape] --> B1[Malicious Code Inserted] B1 --> C1[Database Reads Malicious Code] C1 --> D1[Leak or Unauthorized Access]

4. Buffer Overflow

Let's say Alice has a little cup that can hold 5 candies. Bob tries to stuff 10 candies into that cup. Candies spill everywhere, making a huge mess. In a computer, that's a buffer overflow. If software expects 5 bits of data but gets 10, things can overflow and cause the program to behave in a weird or dangerous way, letting Bob potentially sneak in to do bad things.

flowchart TD AA[Program Expects 5 Bytes] --> BB[Program Receives More Than 5 Bytes] BB --> CC[Overflow Occurs] CC --> DD[Possible Crash or Exploit]

5. Social Engineering Vulnerabilities

Sometimes Bob might just trick Alice into giving him the secret door key. Maybe he pretends to be her friend or sends her a pretend letter from her dad asking for the house key. That is social engineering. Instead of hacking the computer code, Bob hacks Alice's trust. Phishing emails are a common trick, just like a fake letter but in computer shape.

flowchart TD A[Bob] --> B[Creates Fake Email/Call] B --> C[Pretends to be IT Support] C --> D[Asks Alice for Password] D --> E[Alice Shares Credentials] E --> F[Unauthorized Access]

6. Denial of Service (DoS)

Think about if Bob stood in front of Alice's door and blocked anyone from going in or out. He is not really sneaking in, but he's stopping Alice from using her house. In computer terms, that's a denial of service. Attackers send a lot of junk data so the system can't handle it and no one can access the normal services. It's like flooding the house with so many balloons that no one can walk inside.

flowchart TD A[Attacker] --> B[Sends Massive Traffic] B --> C[Server Resources Overwhelmed] C --> D[Legitimate Users Blocked] D --> E[Service Unavailable]

7. Privilege Escalation

Imagine if Bob can only enter the front yard, but he finds a secret staircase to climb up to the attic. The attic is only for special people, but Bob sneaked his way there. That is privilege escalation. He was supposed to have a small key, but now he's got the master key. This can happen when the computer system fails to check who is allowed to do what.

flowchart TD A[Bob: Regular User] --> B[Finds Security Flaw] B --> C[Exploits Vulnerability] C --> D[Gains Admin Access] D --> E[Access to Restricted Data]

All these vulnerabilities can be dangerous in real life. For big companies, including those dealing with sensitive healthcare, government, or personal data, even a small crack can lead to big problems. Regular checks, patches, and strong security controls help keep those cracks smaller or fix them fast.

Frequently Asked Questions

1. What does zero day mean in simple words?

It means nobody knew the hole existed. Hackers find it first, so it's called zero day because there's no time to fix it before it’s used.

2. Why are known vulnerabilities still a threat?

Because some people forget or do not apply patches right away. The cracks are known, but not fixed, so attackers can still use them.

3. What is a patch?

A patch is like a bandage or sticker you put over the hole. In tech, it's code that fixes or repairs a software Vulnerability.

4. Why do misconfigurations happen if they are so easy to fix?

Many people leave default settings or forget to change them. It’s like forgetting to lock your door even if it’s easy to do.

5. What’s the difference between zero day and known vulnerabilities?

A zero day is totally unknown to everyone except attackers. A known Vulnerability is already discovered and recognized.

6. How can social engineering be prevented?

Be careful who you trust. Check emails, do not share passwords, and always confirm who is asking for info.

7. Why do big companies focus on vulnerability management?

They have important data to protect and must follow various security rules. Good management helps keep data safe.

Keywords

Vulnerability classification zero day vulnerabilities zero day attacks vulnerability management data security application security SaaS secure SaaS advanced security cloud-based customer support

About The Author

Ayodesk Publishing Team led by Eugene Mi

Ayodesk Publishing Team led by Eugene Mi

Expert editorial collective at Ayodesk, directed by Eugene Mi, a seasoned software industry professional with deep expertise in AI and business automation. We create content that empowers businesses to harness AI technologies for competitive advantage and operational transformation.

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