Vulnerability scanning tools (Nessus, OpenVAS) in Cybersecurity - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding the primary function of Nessus

What is the main purpose of the Nessus vulnerability scanning tool in cybersecurity?

A To detect and report security vulnerabilities in computer systems and networks

B To encrypt data transmissions between devices

C To act as a firewall blocking unauthorized access

D To monitor user activity and generate usage reports

💡 Hint

Think about what a vulnerability scanner is designed to do.

Nessus is designed to scan systems and networks to find security weaknesses that attackers could exploit.

📋 Factual

intermediate

OpenVAS licensing and availability

Which statement correctly describes OpenVAS in terms of licensing and availability?

A OpenVAS is a proprietary tool requiring paid licenses for all features

B OpenVAS is an open-source vulnerability scanner freely available to users

C OpenVAS is only available as a cloud service with subscription fees

D OpenVAS is a hardware appliance sold by a single vendor

💡 Hint

Consider the meaning of 'open-source' software.

OpenVAS is open-source software, meaning it is free to use and its source code is publicly available.

🔍 Analysis

advanced

Comparing scan results from Nessus and OpenVAS

If a network scan with Nessus reports 10 critical vulnerabilities and the same scan with OpenVAS reports 7 critical vulnerabilities, what could be a reason for this difference?

A Nessus scans are slower, so they find more vulnerabilities by spending more time

B OpenVAS cannot detect critical vulnerabilities due to limited scanning capabilities

C Nessus uses a larger and more frequently updated vulnerability database than OpenVAS

D OpenVAS scans only open ports, while Nessus scans all ports by default

💡 Hint

Think about how vulnerability databases affect scan results.

Nessus often has a more comprehensive and frequently updated database, which can lead to detecting more vulnerabilities.

❓ Reasoning

advanced

Choosing a vulnerability scanner for a small business

A small business wants to implement vulnerability scanning but has a limited budget and no dedicated security team. Which tool is generally more suitable and why?

A OpenVAS, because it is free and open-source, making it cost-effective for small budgets

B Nessus, because it requires no configuration and runs fully automatically without user input

C Nessus, because it is free and open-source like OpenVAS

D OpenVAS, because it provides 24/7 vendor support included with the free version

💡 Hint

Consider cost and ease of use for small teams.

OpenVAS is free and open-source, which helps small businesses with limited budgets. However, it may require some technical knowledge to configure.

❓ Comparison

expert

Interpreting scan output formats

Which output format is commonly supported by both Nessus and OpenVAS for exporting scan results to be used in other security tools?

A PDF, because it allows automated data extraction by security tools

B Plain text, because it is the only format both tools support

C JPEG, because it visually represents vulnerabilities

D XML, because it is a structured format easily parsed by other software

💡 Hint

Think about data formats that are structured and machine-readable.

Both Nessus and OpenVAS support exporting scan results in XML format, which is structured and widely used for data exchange.

Practice

1. What is the main purpose of vulnerability scanning tools like Nessus and OpenVAS?

easy

A. To create new software applications

B. To automatically find security weaknesses in systems

C. To manage user accounts and passwords

D. To encrypt data for secure communication

Solution

1. Step 1: Understand the role of vulnerability scanning tools

   These tools scan computer systems to find security weaknesses automatically.

2. Step 2: Compare options with the tool's purpose

   Only To automatically find security weaknesses in systems describes finding security weaknesses, which matches the tool's main function.

3. Final Answer:

   To automatically find security weaknesses in systems -> Option B

4. Quick Check:

   Vulnerability scanning = find security weaknesses [OK]

Hint: Remember: scanning tools find weaknesses automatically [OK]

Common Mistakes:

• Confusing scanning tools with software development tools
• Thinking they manage user accounts
• Assuming they encrypt data

2. Which of the following commands correctly starts a scan using Nessus from the command line?

easy

A. nessuscli scan start

B. openvas --launch

C. scan nessus begin

D. nessus --start-scan

Solution

1. Step 1: Identify correct command syntax for Nessus CLI

   Nessus uses the command line tool nessuscli with subcommands like scan start to begin scans.

2. Step 2: Check each option

   nessuscli scan start matches the correct syntax. Options A, B, and C are incorrect commands. openvas --launch is for OpenVAS, not Nessus.

3. Final Answer:

   nessuscli scan start -> Option A

4. Quick Check:

   Nessus CLI uses 'nessuscli scan start' [OK]

Hint: Nessus CLI commands start with 'nessuscli' [OK]

Common Mistakes:

• Mixing OpenVAS commands with Nessus
• Using incorrect command order
• Assuming simple flags like '--start-scan' work

3. Consider this simplified output snippet from an OpenVAS scan report:

Host: 192.168.1.10
Vulnerabilities found: 3
 - CVE-2021-1234: High
 - CVE-2020-5678: Medium
 - CVE-2019-0001: Low

What does this output tell you?

medium

A. The scan failed to complete on the host

B. The scan found no vulnerabilities on the host

C. The host is fully secure with no risks

D. The host has three security issues with different severity levels

Solution

1. Step 1: Read the scan report details

   The report lists three vulnerabilities found on the host with severity levels High, Medium, and Low.

2. Step 2: Interpret the meaning of vulnerabilities found

   Since vulnerabilities are listed, the host has security issues. It is not fully secure or failed scan.

3. Final Answer:

   The host has three security issues with different severity levels -> Option D

4. Quick Check:

   Vulnerabilities listed = security issues found [OK]

Hint: Vulnerabilities listed means issues found [OK]

Common Mistakes:

• Ignoring the vulnerability count
• Assuming no vulnerabilities means secure
• Confusing scan failure with vulnerabilities

4. You run an OpenVAS scan but get no results even though you know vulnerabilities exist. Which of these is the most likely cause?

medium

A. The target system is offline

B. OpenVAS does not detect vulnerabilities

C. The scan was run without proper credentials or permissions

D. The scan tool is outdated but still shows results

Solution

1. Step 1: Analyze why no results appear despite known vulnerabilities

   Without proper credentials or permissions, OpenVAS cannot access detailed info to find vulnerabilities.

2. Step 2: Evaluate other options

   OpenVAS does not detect vulnerabilities is false; OpenVAS detects vulnerabilities. The target system is offline would cause scan failure, not empty results. The scan tool is outdated but still shows results contradicts showing results.

3. Final Answer:

   The scan was run without proper credentials or permissions -> Option C

4. Quick Check:

   Missing credentials = no vulnerability data [OK]

Hint: No results often mean missing permissions [OK]

Common Mistakes:

• Assuming OpenVAS never detects vulnerabilities
• Confusing offline system with empty results
• Ignoring credential requirements

5. You want to schedule regular vulnerability scans on your network using Nessus. Which approach best ensures continuous security monitoring?

hard

A. Set up automated scheduled scans with email alerts for new vulnerabilities

B. Run manual scans only when a security breach is suspected

C. Disable scans to avoid network slowdowns

D. Scan only once a year during audits

Solution

1. Step 1: Understand best practices for vulnerability scanning

   Regular automated scans with alerts help detect new issues early and maintain security.

2. Step 2: Compare options for continuous monitoring

   Set up automated scheduled scans with email alerts for new vulnerabilities supports continuous monitoring. Options B, C, and D delay detection or reduce security.

3. Final Answer:

   Set up automated scheduled scans with email alerts for new vulnerabilities -> Option A

4. Quick Check:

   Automated scheduled scans = continuous security [OK]

Hint: Automate scans with alerts for best security [OK]

Common Mistakes:

• Waiting for breaches before scanning
• Disabling scans to save resources
• Scanning only during audits