Network Security Related Issues

Here are a few sample questions when it comes to written interview questions about understanding popular network security devices and defenses:

Please list some mainstream network security appliances and briefly describe their functions and uses.
What is a firewall? Describe the basic working principles and common deployment methods of firewalls.
Please explain what an intrusion detection system (IDS) and an intrusion prevention system (IPS) are, and describe how they differ and how they work.
What is a Virtual Private Network (VPN)? Describe the role of VPN and common VPN connection methods.
Please introduce some common authentication and access control technologies, such as single-factor authentication, two-factor authentication, and multi-factor authentication.

These questions will test the candidate's knowledge of mainstream network security devices and defense mechanisms, as well as their understanding of their functions, working principles and application scenarios. When answering questions, candidates can use specific examples and scenarios to deepen understanding and explanation of the concepts.

1. Please list some mainstream network security devices and briefly describe their functions and uses

Firewall: firewall, monitoring and controlling network traffic, used for access control policies, preventing unauthorized access and network attacks
Virtual private network VPN, providing secure remote access and data transmission channels, through encryption and tunneling technology, to establish a private connection on the public network
Load Balancer, balance and distribute network traffic, improve system performance and availability, prevent malicious attacks and denial of service attacks
IDS intrusion detection system, monitors abnormal activities in the system, generates alarms and logs, and discovers potential security threats
The IPS intrusion prevention system has the capability of active response and can actively block the detected intrusion behavior.

2. What is a firewall, its working principle and common deployment methods

A firewall is a network security device that monitors and controls traffic, performs access control according to predefined rules, and prevents unauthorized network attacks
Working principle: Check and filter network data packets according to predefined rules. The filtering rules include source address, destination address, port number, network protocol, etc. to make decisions. Allow or block certain types of packets through
Common deployment methods: network layer firewall, host firewall, cloud firewall

3. Please explain what an intrusion detection system (IDS) and an intrusion prevention system (IPS) are, and describe the difference between them and how they work

Intrusion Detection System (IDS), monitors and detects abnormal activities and behaviors in the system, analyzes logs and system events, and generates warnings
Intrusion prevention system IPS, with active response capability, proactively prevents intrusion behavior
IDS is used for monitoring and alarming, IPS is active defense and response capabilities
Working principle: IDS monitors network traffic, system logs and events, and uses rules, signatures, and behavior analysis techniques to identify potential intrusion behaviors; IPS adds a defense and response mechanism on the basis of IDS, and detects intrusions according to preset Rules, which can actively block attacks;

4. What is a VPN

A virtual private network (VPN) is a technology for establishing a secure connection over a public network, such as the Internet. It creates a virtual, private communication channel over an unsecured public network by using encryption and tunneling techniques

The role of a VPN includes:

Remote Access: Allows users to securely connect to a company or organization's internal network over a public network
Confidential communication: Through encryption technology, the transmission process of sensitive data on the public network is protected to prevent data from being stolen or tampered with.
Bypass Internet Restrictions: Bypass geo-location restrictions, web censorship or blocking and access restricted content and services by connecting to a VPN server located in a different geographical location

5. Please introduce some common authentication and access control technologies, such as single-factor authentication, two-factor authentication and multi-factor authentication

Single-factor authentication: users only need to provide one factor authentication identity, usually username and password
Two-factor authentication: users need to provide knowledge factors and possession factors for authentication, and possession factors can be verification codes
Multi-factor authentication: knowledge, possession, and characteristic factors authenticate identity. Biometrics such as fingerprints, irises, location factors, etc. improve security
SSO single sign-on, one login to access all authorized systems
ACL access control list, the administrator configures rules to control the user's access to specific resources

6. Discuss the difference and connection between XSS attacks and CSRF (Cross Site Request Forgery).

the difference:

XSS attacks use malicious scripts to inject users' browsers to attack users by tampering with web page content or performing malicious operations. The target of the attack is the user's browser, mainly for the theft or tampering of the user's personal information and session information.
CSRF attacks exploit a user's authenticated session to perform unintended actions without the user's knowledge. The target of the attack is the web application that the victim has logged in, and it is mainly used to perform malicious operations, such as changing passwords, posting comments, etc.

connect:

XSS attacks can provide possible attack vectors for CSRF attacks. By injecting malicious scripts in the compromised website, the attacker can exploit the victim's browser to perform a CSRF attack.
CSRF attacks can exploit XSS vulnerabilities for more effective attacks. Malicious code can perform CSRF attacks on the victim's behalf by enticing the victim to visit a specific web page.

7. Provide a scenario and explain how to prevent XSS attacks during the design and development stages

Input Validation and Filtering
output encoding
Set the cookie to the httponly attribute
Safety Education and Training
Regularly update and patch vulnerabilities: Timely update and patch the software and frameworks used by the website, including web servers, databases, and applications. Timely repair of vulnerabilities can reduce the possibility of being attacked.
Use a Web Application Firewall (WAF): Deploying a WAF can help detect and block potential XSS attacks. A WAF can monitor incoming requests and responses and identify and block malicious activity based on a predefined set of rules.
Security Code Review: Conduct regular security code reviews to check for potential XSS vulnerabilities in applications. Identify and fix possible security issues by carefully reviewing and testing the code.
Continuous monitoring and logging: Establish an effective monitoring and logging mechanism to discover and respond to XSS attacks in a timely manner. Monitor network traffic, user behavior, and anomalous activities to identify and respond to potential attacks in a timely manner.

8. What is a DDos attack and how to prevent it

A DDoS (Distributed Denial of Service) attack is a malicious act designed to make the system unable to work properly or provide services to legitimate users by sending a large number of requests or network traffic to the target system at the same time, so that it exceeds the carrying capacity. Here is a further explanation of the DDoS attack:

Attack principle: DDoS attacks take advantage of the resource limitations of the target system. By launching a large number of requests or network traffic at the same time, bandwidth, CPU, memory or other system resources are occupied, resulting in slow system response, service unavailability or complete paralysis.
Attack type:
- Bandwidth-consuming attacks: By sending a large amount of network traffic, the bandwidth resources of the target system are exhausted.
- Connection consumption attack: By establishing a large number of connection requests, the connection resources of the target system are exhausted.
- Application layer attack: Flood attacks targeting application vulnerabilities or specific requests prevent the target system from processing requests normally.
- Reflection amplification attack: Use servers or services with reflection attacks to amplify the attack traffic and direct it to the target system, thereby increasing the attack power.
Defense method:

Traffic Filtering and Firewall: Configure network devices, firewalls, or intrusion prevention systems to filter and block malicious traffic.
Load balancing: use load balancing devices to disperse traffic, ensure that system resources are utilized reasonably, and avoid single points of failure.
CDN (Content Distribution Network): Use CDN services to distribute traffic, distribute attack traffic to different nodes, and reduce the burden on the target system.
Traffic cleaning: Through the traffic cleaning service, malicious traffic is detected and filtered, and only legitimate traffic is passed to the target system.
High-availability architecture: use redundant servers and devices to ensure high availability of the system and to resist part of the attack traffic.
Restrict connections and requests: Set connection and request restriction policies to prevent abnormally frequent connections or requests.
Security Monitoring and Alerting: Implement a real-time security monitoring and alerting system to detect and respond to DDoS attacks in a timely manner.

9. What is a good security solution?

A good security program is an integrated, comprehensive, and effective approach and strategy designed to protect systems, networks, and data from a variety of threats and attacks. Here are some key points of a well-built security solution:

Security Awareness and Training: Establish and cultivate security awareness within the organization, ensuring that all users are aware of security best practices and policies, and receive regular security training.
Risk assessment and management: conduct a comprehensive risk assessment of systems and networks, identify potential threats and vulnerabilities, and formulate corresponding risk management strategies and plans.
Multi-layer defense: adopt multi-layer defense measures, including network firewall, intrusion detection and prevention system (IDS/IPS), anti-virus software, security audit and monitoring, etc., to provide multiple protection and defense.
Strengthen authentication and access control: Implement strong authentication mechanisms, such as two-factor authentication and multi-factor authentication, and strict access control policies to ensure that only authorized users can access sensitive resources.
Security audit and monitoring: Establish a security audit and monitoring system to track and record key system and network activities, and detect and respond to potential security incidents and intrusions in a timely manner.
Data protection and backup: Adopt appropriate data encryption, backup and recovery strategies to ensure data integrity, availability and confidentiality, and prevent data loss and disclosure.
Vulnerability management and patch update: regular vulnerability scanning and vulnerability management, timely installation of system and application patches and security updates, and repair of known security vulnerabilities.
Emergency Response and Recovery Plan: Develop an emergency response plan and recovery strategy, including steps to deal with security incidents and intrusions, methods for restoring systems and services, and communication and cooperation with relevant parties.
Compliance and Regulatory Compliance: Ensure compliance with applicable security standards, regulations and compliance requirements such as GDPR, HIPAA, PCI DSS and more.
Regular audit and improvement: conduct regular security audit and assessment, discover and correct security problems and improvement opportunities, and continuously improve the effectiveness and efficiency of the security program.

What is IDC

IDC is the abbreviation of Internet Data Center (Internet Data Center), which is a specialized facility that provides services such as data storage, processing, management and network connection. IDCs are usually built and operated by large enterprises, service providers or specialized data center operators to host customers' servers, network equipment and related facilities.

The main functions of IDC include the following aspects:

Equipment hosting: IDC provides safe and reliable equipment hosting services. Customers can place their own servers and network equipment in IDC's computer room to take advantage of its high-speed, stable network connection and high-quality environmental conditions.
Cloud computing and virtualization: IDC provides cloud computing and virtualization services. Through virtualization technology, physical servers are divided into multiple virtual machines, so that customers can flexibly manage and use computing resources.
Data storage and backup: IDC provides large-capacity data storage devices and backup services to help customers store and protect important data and prevent data loss or damage.
Network access and interconnection: IDC provides high-speed and stable network access and interconnection services to ensure that customers' servers and network devices can communicate reliably with the Internet and other data centers.
Security and monitoring: IDC is equipped with advanced security equipment and monitoring systems to ensure the security of customers' equipment and data, monitor the operating status of equipment, and discover and respond to potential security threats in a timely manner.
Power and environmental management: IDC provides reliable power supply and environmental control, including cooling system, fire extinguishing system, UPS (uninterruptible power supply), etc., to ensure the normal operation of equipment and maintain appropriate temperature and humidity.

By using IDC's services, enterprises and organizations can hand over the management and operation and maintenance of IT infrastructure to professional institutions, saving costs, improving efficiency, and obtaining a more reliable and secure data processing and storage environment.

When interviewing a network security engineer, here are some possible written and interview questions covering basic security configurations and policies:

Pen questions:

List several common password attacks and describe how to defend against them.

Common password attack methods include brute force cracking, dictionary attack, rainbow table attack, etc. Defenses against these attacks include strong password policies, password hashing and salting, and the use of multi-factor authentication.

b. Explain the role and basic principles of firewalls, as well as common types of firewalls

The role of the firewall is to monitor and filter network traffic, and decide to allow or deny the passage of data packets based on predefined rules or policies. Common types of firewalls are network layer firewalls, application layer firewalls, and next-generation firewalls

c. Explain what key management is, and list several common key management methods

Key management is the process of managing and protecting the keys used in encryption algorithms. Common key management methods include key generation, distribution, storage, and update, such as using key management systems, key storage, and key rotation.

d. Describe the concept and purpose of network isolation, and list several methods to achieve network isolation

Network isolation is to divide the network into different areas to limit the propagation range of network traffic and reduce the attack surface. Common methods for implementing network isolation include virtual local area network (VLAN), subnetting, and physical isolation.

e. Explain what a reverse proxy and a forward proxy are, and compare their differences

Both reverse proxy and forward proxy are used to handle requests and responses between clients and servers. The difference is that the reverse proxy provides services to the client on behalf of the server, while the forward proxy requests services from the server on behalf of the client

Interview questions:

15. How have you implemented basic security configurations and policies in your previous work experience?

In my previous work experience, I implemented basic security configurations and policies by implementing strong password policies, access control lists, and firewall rules. At the same time, I regularly review and update system and application security patches, conduct network monitoring and incident response, and train users on security awareness.

16 Please list several basic security configuration items of operating systems or network devices that you are familiar with

The basic security configuration items of some operating systems or network devices include closing unnecessary services, enabling firewalls, using secure encryption protocols, restricting remote access, etc.

17 How to ensure security updates and patch management for servers?

I will establish a security update and patch management process, including regular inspection of security updates and patches released by manufacturers, and after testing and verification, deploy them to the production environment in time to fix known security vulnerabilities

18. What are your experiences and approaches to protecting sensitive data?

When it comes to protecting sensitive data, here are some common lessons and approaches:

Data Classification and Labeling: Classify and label sensitive data to determine its security level and access rights. This helps ensure that appropriate safeguards are applied to sensitive data.
Data Encryption: Sensitive data is encrypted using a suitable encryption algorithm. Encryption provides an extra layer of protection during data transmission and storage, making it difficult to understand and use even if the data is accessed by unauthorized persons.
Access Control: Implement strict access control policies to ensure only authorized users can access sensitive data. This includes authentication, authorization and rights management to ensure only those who need to can view and modify data.
Auditing and monitoring: Establish a logging and monitoring mechanism to audit the access and operation of sensitive data. This helps spot unusual activity, unauthorized access, and potential security threats.
Data backup and recovery: regularly back up sensitive data and ensure the security of the backup data. In the event of data corruption, disasters or security incidents, data can be recovered in time to ensure business continuity.
Employee Training and Security Awareness: Enhance employee security awareness and training to understand the value and protection of sensitive data. Employee security awareness and behavior are critical to keeping sensitive data safe.
Security compliance and standards: Follow relevant security compliance standards and best practices such as PCI DSS, ISO 27001, etc. These standards provide guidance and a framework for protecting sensitive data.

These are some common experiences and approaches for protecting sensitive data and ensuring its confidentiality, integrity, and availability. In practice, specific methods and measures should be customized and implemented according to the needs of the organization and the business environment.

19 How will you respond and deal with security incidents or vulnerabilities?

When faced with security incidents or vulnerabilities, I will take the following countermeasures and handling measures:

Immediate Response: Detect and confirm security incidents or vulnerabilities in a timely manner, and take immediate action to reduce the scope of damage.
Isolation and Recovery: Isolate the affected system or network to prevent further spread and perform necessary recovery operations such as system repair, data recovery, etc.
Collect evidence: Record and collect evidence related to security incidents or vulnerabilities for subsequent investigation and analysis.
Notify relevant parties: Report security incidents to internal teams, management and relevant partners in a timely manner, and cooperate with relevant agencies or third parties for necessary notification and cooperation.
Vulnerability repair: Perform detailed analysis and evaluation on the discovered vulnerabilities, and repair or patch the vulnerabilities in time to prevent them from being exploited again.
Post-event summary and improvement: Conduct post-event summary and analysis of security incidents to understand the root causes and causes of vulnerabilities, and take corresponding measures to strengthen defense capabilities and security measures.

The answers above demonstrate an understanding of basic security configurations and policies as well as experience in practice. Candidates' responses should demonstrate their depth of knowledge and ability to respond to security incidents. You can drill down further to discuss their real-world experiences, problem-solving approaches, and attitude toward continuous learning and improvement.