web attack interview | network penetration interview (2)

Web Attack Interview Outline

1. Common Web Attack Types
1.1 SQL Injection Attack
SQL injection attack is a common type of Web attack, which exploits the incorrect processing of user input data by Web applications, allowing attackers to execute malicious SQL statements. By injecting malicious SQL code, an attacker can bypass the application's authentication and authorization mechanisms and gain unauthorized access.
SQL injection attacks usually occur in web applications that interact with databases. Attackers insert malicious SQL statement fragments into the data entered by the user, thereby changing the logic of the original SQL query statement. These malicious SQL statements can cause the database to perform unauthorized operations, such as deleting, modifying or leaking sensitive data.

Attackers can use various methods to carry out SQL injection attacks, including but not limited to:

• Error-based injection: The attacker constructs malicious input data to trigger the application to generate SQL syntax errors, thereby obtaining sensitive information about the database structure and data.

• Injection based on Boolean blind injection: The attacker constructs malicious input data and uses the application's different responses in the query results to infer database information.

• Time-blind injection: The attacker constructs malicious input data and uses the application's different response times in query results to infer database information.

• Injection based on union query: The attacker constructs malicious input data and uses the UNION operator to merge the malicious query results into the original query results to obtain additional data.

To prevent SQL injection attacks, developers should take the following measures:

• Use parameterized queries or prepared statements to ensure that user-entered data is not interpreted as SQL code.

• Perform strict validation and filtering of user-entered data to ensure that only data in the expected format is accepted.

• Minimize database user permissions and avoid using database accounts with excessive permissions.

• Database and application security vulnerabilities are regularly updated and patched to prevent attackers from exploiting known vulnerabilities to conduct injection attacks.

  By understanding how SQL injection attacks work and how to prevent them, web developers can better protect their applications from this common type of web attack.

1.2 XSS attack
XSS attack is one of the common types of web attacks. It refers to a cross-site scripting attack (Cross-Site Scripting), in which attackers inject malicious scripts into web applications so that users can execute these scripts in the browser to achieve the purpose of the attack.

XSS attacks can be divided into three types: stored XSS, reflected XSS and DOM-based XSS. Stored XSS means that attackers store malicious scripts on the server side, and when users visit pages containing these scripts, the scripts will be executed. Reflected XSS means that attackers inject malicious scripts as parameters into URLs. When users click on URLs containing these scripts, the scripts will be executed. DOM-based XSS means that the attacker modifies the DOM structure of the page and injects malicious scripts to achieve the attack.

XSS attacks are very harmful. They can lead to the theft of users' sensitive information, account theft, malicious operations, etc. To prevent XSS attacks, developers should strictly filter and validate user input and avoid inserting user input directly into HTML pages. Common defense measures include escaping special characters, using safe encoding methods, limiting the length and format of user input, etc.

In summary, XSS attack is a common type of web attack, which is carried out by injecting malicious scripts. Developers should take appropriate defensive measures to protect the security of web applications and users.

1.3 CSRF attack
CSRF attack is one of the common types of web attacks. It refers to a cross-site request forgery attack, in which an attacker sends a malicious request to a target website by forging user identity information to achieve the purpose of the attack. CSRF attacks take advantage of the imperfect authentication of users by websites. By enticing users to click malicious links or visit malicious webpages, attackers can perform malicious operations without the user's knowledge, such as modifying user information and initiating transfers. In order to prevent CSRF attacks, websites can take some measures, such as using randomly generated tokens to verify user requests, detecting Referer headers, etc.

1.4 Command injection attack
Command injection attack is a common type of web attack, which exploits the insufficient validation and filtering of user input by web applications. The attacker inserts malicious commands into the data entered by the user, causing the web application to execute the attacker's preset commands when executed. This type of attack can lead to serious security vulnerabilities, possibly leading to complete control of the system or leakage of sensitive information.

Command injection attacks typically occur where a user is required to enter a command, such as a command line interface or the ability to execute system commands through a web application. An attacker can bypass an application's input validation by inserting special characters or command syntax into user input. Once the attack is successful, the attacker can execute any system commands, including deleting, modifying or obtaining system files, executing malicious code, etc.

To prevent command injection attacks, developers should implement strict validation and filtering of user input. First, input validation should be performed on user input to ensure that the entered data conforms to the expected format and type. Secondly, user input should be filtered to filter out special characters and command syntax, or the input should be escaped. Most importantly, developers should use parameterized queries or precompiled statements to execute system commands instead of directly splicing user-entered data.

In addition to the responsibility of developers, users should also be vigilant and avoid entering sensitive information or executing system commands in untrusted websites or applications. At the same time, regularly updating and maintaining system security patches, and using tools such as firewalls and security software are also important measures to prevent command injection attacks.

In a word, command injection attack is a common type of web attack. Both developers and users should strengthen the awareness of preventing such attacks and take corresponding security measures to protect the security of the system and users.
2. SQL Injection Attacks
2.1 Basic Concepts
SQL injection attacks are a common web application security vulnerability, which exploits the incorrect processing of user input data by the application, thereby allowing attackers to execute malicious SQL statements. By successfully exploiting SQL injection vulnerabilities, attackers can bypass the application's authentication, access and modify sensitive information in the database, or even completely control the entire database.

In a SQL injection attack, the attacker usually inserts malicious SQL code into the data entered by the user to achieve the purpose of the attack. These malicious codes can be part of a SQL query statement, a SQL command, or even the entire SQL statement. When an application fails to properly filter, escape, or validate user input, attackers have the opportunity to inject malicious code and perform their desired actions.

SQL injection attacks can be divided into different types, including error-based injection, union query injection, Boolean blind injection, etc. Attackers can exploit these different types of injection vulnerabilities to obtain sensitive information, modify database contents, execute arbitrary commands, etc.

In order to effectively defend against SQL injection attacks, developers should take a series of security measures. First, user input should be strictly verified and filtered to ensure that only legal input data is accepted. Second, SQL queries should be constructed using parameterized queries or prepared statements to avoid splicing user input directly into the SQL statement. Additionally, database users should be limited in their privileges to ensure they can only perform necessary operations, and applications and databases should be regularly updated and patched with security patches.

By understanding the basic concepts of SQL injection attacks, developers can better understand and identify potential vulnerabilities and take appropriate measures to protect the security of web applications.

2.2 Attack principle

SQL injection attack is a common web attack method, which uses the improper processing of user input data by web applications, and inserts malicious SQL codes into the user input data to achieve illegal access and operation of the database. By constructing specific SQL statements, the attacker makes the application perform unexpected operations when executing database queries, such as bypassing authentication, obtaining sensitive information, modifying data, or deleting data in the database.

The principle of SQL injection attack is mainly to use the application's trust in the user's input data. When the application does not fully verify and filter the user's input, the attacker can deceive the application to execute unexpected SQL by constructing malicious input data. operate. An attacker can change the logic of the original SQL query statement by inserting special characters, SQL keywords, or SQL statement fragments into the input data, thereby bypassing the security mechanism of the application.

Attackers can use SQL injection vulnerabilities to perform various malicious operations, such as injecting malicious SQL statements to obtain sensitive information in the database, such as usernames, passwords, credit card information, etc. Attackers can also modify the data in the database by injecting malicious SQL statements, such as tampering with user account information, deleting data in the database, or inserting malicious data. In addition, attackers can also use SQL injection vulnerabilities to conduct further attacks, such as obtaining database permissions to further attack other systems or servers.

In order to prevent SQL injection attacks, developers should fully verify and filter the data entered by users to ensure the legality and security of the input data. Common defensive measures include using parameterized queries or precompiled statements to prevent SQL injection attacks, strict validation and filtering of user input, restricting database user privileges, regularly updating and patching database software, etc. At the same time, developers should also keep abreast of the latest security vulnerabilities and attack techniques, and update and improve the security mechanism of the application in time to improve the security of the application and the ability to resist SQL injection attacks.

2.3 Defense measures

In the Web Attack Interview Outline, SQL injection attacks are a common security threat. In order to effectively defend against SQL injection attacks, the following are some important defensive measures:

1. Input verification and filtering: Strict verification and filtering should be performed on data entered by users to ensure that only legal input is accepted. This can be achieved by using techniques such as regular expressions, whitelist filtering, etc.

2. Use parameterized queries: Parameterized queries are an effective way to defend against SQL injection attacks. By passing user-entered data as parameters to the query statement, rather than splicing it directly into the query statement, you can prevent attackers from using the input to modify the query logic.

3. Principle of Least Privilege: In the configuration of the database, the principle of least privilege should be used for applications. That is, providing the application with the minimum permissions necessary to perform the necessary actions to reduce the attack surface that an attacker could exploit.

4. Error message handling: In applications, you should avoid displaying detailed error messages to the user, especially error messages about the database. An attacker can use this information to obtain sensitive information about the database structure and query statements.

5. Regular updates and maintenance: Updating database software and applications is one of the important measures to maintain security. Apply security patches and updates promptly to fix known vulnerabilities and weaknesses.

6. Security audit and monitoring: Establish a security audit and monitoring mechanism to monitor and record database access and operations. In this way, abnormal behavior can be detected in time and corresponding measures can be taken.

By taking these defensive measures, you can effectively reduce the risk of SQL injection attacks and protect the security of web applications and databases. However, it should be noted that these measures are not absolute. It is still necessary to constantly pay attention to the latest security threats and vulnerabilities, and to update and adjust defense strategies in a timely manner.

3. XSS attack

3.1 Basic Concepts
XSS attacks are an important topic in the Web Attack interview syllabus. In this section, we will introduce the basic concepts of XSS attacks to help readers better understand and deal with this common network security threat.

XSS (Cross-Site Scripting) attack is an attack method that exploits security vulnerabilities in web applications to inject malicious scripts into the user's browser. By inserting malicious scripts into web pages visited by victims, attackers can steal users' sensitive information, tamper with web content, and even control users' browsers.

In XSS attacks, attackers often exploit a web application's inadequate filtering and validation of user input to carry out the attack. Common XSS attack types include stored XSS, reflected XSS and DOM-based XSS.

A stored XSS attack occurs when an attacker stores a malicious script in the database of a web application. When other users access the page containing the malicious script, the malicious script will be executed. This attack method is common in scenarios where user input needs to be stored, such as message boards and comment functions.

Reflected XSS attacks occur when attackers pass malicious scripts as parameters to web applications by convincing users to click on malicious links or visit specific URLs. When the web application returns a response, it inserts malicious scripts into the response page to achieve the purpose of the attack. This attack method is common in search functions, URL jumps and other scenarios.

DOM-based XSS attack means that the attacker modifies the DOM structure of the page and injects malicious scripts into the page to achieve the purpose of the attack. This attack method is common in applications that use JavaScript to dynamically modify page content.

In order to prevent XSS attacks, developers should fully filter and verify user input and avoid inserting unprocessed user input directly into the page. Common defense measures include using safe encoding methods, escaping user input, restricting the use of special characters, etc.

By understanding the basic concepts of XSS attacks, readers can better understand this common web security threat and take corresponding defensive measures to protect the security of their own web applications and users.

3.2 Attack Principle
XSS attack is a common Web attack method. It takes advantage of the web application's trust in user input and injects malicious script code to achieve the purpose of the attack. Attackers can obtain users' sensitive information, hijack user sessions, tamper with web content, etc. by injecting malicious scripts into web pages visited by victims.

The principle of XSS attack mainly includes the following aspects:

1. Attackers take advantage of the web application's trust in user input to implement attacks by injecting malicious script code into web pages. These malicious scripts can be code written in JavaScript, HTML, or other scripting languages.

2. Attackers usually exploit security vulnerabilities in web applications, such as failure to properly filter user input and failure to properly encode output, to inject malicious scripts.

3. Once a user visits a webpage injected with malicious script, the malicious script will be executed in the user's browser. At this time, attackers can use malicious scripts to obtain users' sensitive information, such as user names, passwords, etc., or deceive users by tampering with web page content.

4. XSS attacks can be divided into three types: storage type, reflection type and DOM type. Stored XSS attacks store malicious scripts on the server side. When a user accesses a page containing malicious scripts, the malicious scripts are loaded and executed from the server side. Reflected XSS attacks attach malicious scripts as parameters to the URL. When the user clicks on the URL containing the malicious script, the malicious script will be extracted from the URL and executed. DOM-type XSS attacks trigger the execution of malicious scripts by modifying the DOM structure of web pages.

5. Methods to defend against XSS attacks include input filtering and output encoding. Input filtering refers to filtering and verifying data entered by users to ensure that only legal input is accepted. Output encoding refers to encoding special characters when outputting user-entered data to a web page to prevent the execution of malicious scripts.

By understanding the principles of XSS attacks, we can better understand its harm and defense methods, thereby improving the security of web applications.

3.3 Defense measures
XSS attack is a common attack method in the field of Web security. It takes advantage of the incomplete trust of user input by web applications and injects malicious script code to achieve the purpose of attack. In order to effectively defend against XSS attacks, the following are some common defense measures:

1. Input filtering and verification: Filter and verify the data entered by users to ensure that only legal input is accepted. You can use a whitelist mechanism to only allow specific characters and formats to pass verification to filter out potentially malicious code.

2. Output encoding: When outputting user-entered data to a web page, special characters are encoded and converted into safe character entities to prevent the execution of malicious scripts. Common encoding methods include HTML entity encoding, URL encoding, etc.

3. Use HTTP-only Cookies: Store sensitive information in HTTP-only Cookies, restrict JavaScript access rights, and prevent XSS attackers from stealing user identity authentication information.

4. Content Security Policy (CSP): By setting a CSP policy, you can limit the resources that can be loaded and the scripts that can be executed in web pages to prevent the injection and execution of malicious scripts.

5. Safe development practices: During the development process, it is necessary to follow safe coding standards, avoid using unsafe functions and methods, try to use safe APIs and frameworks, and repair known security vulnerabilities in a timely manner.

6. Regular updates and maintenance: Timely update and maintain relevant components and libraries of web applications, including web servers, databases, frameworks, etc., to fix known security vulnerabilities and improve system security.

By taking the above defensive measures, you can effectively reduce the risk of XSS attacks and protect the security of web applications and users.

4. CSRF Attack
   4.1 Basic Concepts
   CSRF attack is an important topic in the Web Attack interview syllabus. In this section, we will introduce the basic concepts of CSRF attacks. CSRF (Cross-Site Request Forgery) cross-site request forgery is an attack method that uses users to perform unexpected operations on authenticated websites. The attacker uses the victim's identity and permissions to perform a series of unauthorized operations by convincing the victim to perform malicious requests in the browser. This attack method usually takes advantage of the website's trust in user requests, and by forging the source of the request, the server cannot distinguish between legitimate requests and malicious requests. CSRF attacks are a serious security threat to web applications, so it is very important to understand its basic concepts and defensive measures.

4.2 Attack Principle
CSRF attack is a common web attack method, which uses the user's authentication information when accessing a trusted website. Attackers achieve their attack goals by constructing malicious requests to induce users to perform certain operations on trusted websites. The principles of CSRF attacks mainly include the following aspects:

1. Utilize authentication of trusted websites: Attackers masquerade as legitimate users by obtaining user authentication information on trusted websites, such as cookies.

2. Constructing malicious requests: Attackers use the obtained authentication information to construct malicious requests, including the URL and parameters of the target website, to achieve the purpose of attack.

3. Inducing users to perform operations: Attackers use various means, such as sending phishing emails, injecting malicious advertisements, etc., to induce users to click on malicious links or visit malicious websites, thereby triggering malicious requests.

4. Bypass the same-origin policy: Since CSRF attacks are cross-site request forgery, the attacker needs to bypass the browser's same-origin policy, that is, send requests under different domain names. Common bypass methods include using images, Flash, jumps, etc.

5. Steal user information or perform malicious operations: Once a user executes a malicious request constructed by an attacker on a trusted website, the attacker can obtain the user's sensitive information, such as account password, or perform some malicious operations, such as modifying user settings, Initiate transfers, etc.

Summary: CSRF attacks use the user's authentication information when accessing a trusted website to achieve the purpose of the attack by constructing malicious requests and inducing users to perform operations. In order to prevent CSRF attacks, website developers can take some measures, such as using CSRF tokens, checking the Referer header, restricting sensitive operations, etc.

4.3 Defense Measures
CSRF attack is a common web security threat, which utilizes the authentication information of users when visiting trusted websites. In order to effectively defend against CSRF attacks, the following are some common defense measures:

1. Random Token: Includes a randomly generated token with each user request that is associated with the user session. The server verifies the validity of the token when it receives the request and rejects the request if the token is invalid. This approach prevents attackers from forging requests.

2. Double Submit Cookie (Double Submit Cookie): When the user logs in, the server will generate a random token and store it in the user's Cookie. In each request, the token is sent to the server in the form of a cookie and request parameters. The server compares the two tokens to see if they are consistent, and if they are inconsistent, rejects the request.

3. Verify HTTP Referer: The server can determine whether the source of the request is legal by verifying the Referer field of the request. Only if the request's Referer field matches the value expected by the server will the request be processed. This approach prevents attackers from launching CSRF attacks through third-party websites.

4. Verification code (CAPTCHA): Users are required to enter a verification code before key operations (such as changing passwords, deleting accounts, etc.). The verification code is usually a picture containing random characters, and the user needs to enter the characters in the picture correctly to continue. This approach prevents automated scripts from launching CSRF attacks.

5. SameSite attribute: When setting a cookie, you can use the SameSite attribute to limit the sending of the cookie. The SameSite attribute has three values: Strict, Lax, and None. Strict means that cookies will only be sent under the same site, Lax means that cookies will only be sent in cross-site secure requests, and None means that cookies will always be sent. By setting the SameSite attribute to Strict or Lax, you can effectively reduce the risk of CSRF attacks.

6. Frequent token rotation (Token Rotation): Regularly changing the token in a user session can make it more difficult for an attacker to guess the token. When a user performs a sensitive operation, the server generates a new token and updates it to the user's session.

The above are some common measures to defend against CSRF attacks. By taking these measures, web applications can be effectively protected from the threat of CSRF attacks.

5. Command injection attack
   5.1 Basic concepts
   Command injection attack is a common web attack method. It takes advantage of the application's insufficient verification and filtering of user input, allowing attackers to inject malicious commands into the application. This type of attack typically occurs in applications that interact with a database or operating system.

In a command injection attack, an attacker inserts special characters or commands into user input to perform illegal operations or gain unauthorized access. Attackers can use this vulnerability to perform various malicious operations, such as executing system commands, accessing sensitive data, modifying database contents, etc.

To prevent command injection attacks, developers should implement strict validation and filtering of user input. First, user input should be subject to input validation to ensure that only expected data types and formats are accepted. Secondly, user input should be output filtered and special characters should be escaped or deleted to prevent the injection of malicious commands.

Additionally, developers should use parameterized queries or prepared statements to perform database operations rather than directly splicing user-entered data. This can effectively prevent command injection attacks.

In short, command injection attacks are a common web attack method. Developers should be aware of this threat and take corresponding protective measures to protect the security of applications and users.

5.2 Attack Principle
Command injection attack is a common Web attack method. It takes advantage of the application's insufficient verification and filtering of user input, allowing the attacker to inject malicious commands into the execution environment of the application. In this way, the attacker can execute arbitrary system commands to obtain sensitive information, control the server, or damage the system.

The principle of command injection attack mainly takes advantage of the application's trust in user input. The attacker inserts specific command statements into the data entered by the user, so that the application will execute these commands as legal instructions when executing. This attack method usually occurs in scenarios that require the user to input data and execute it as a command. For example, the user enters a command and submits it to the server for execution, but the server does not fully validate and filter the user input during execution.

Attackers can conduct command injection attacks in different ways. One common way is to bypass the application's input validation by inserting special characters or command delimiters into user input. Attackers can use these special characters to construct malicious command statements to execute arbitrary system commands. In addition, attackers can also take advantage of the application's incomplete trust in user input and bypass input validation by constructing specific input data to achieve command injection attacks.

To prevent command injection attacks, developers need to adequately validate and filter user input. First, input validation should be performed on user input to ensure that the entered data conforms to the expected format and range. Secondly, user input should be output filtered and special characters should be escaped or deleted to prevent the injection of malicious commands. In addition, you can also use parameterized queries or use secure APIs to execute system commands to reduce the risk of command injection.

In short, command injection attack is a common web attack method, in which attackers execute arbitrary system commands by injecting malicious commands into user input. To prevent such attacks, developers need to adequately validate and filter user input, and take corresponding security measures to reduce the risk of command injection.

5.3 Defense Measures
Command injection attack is a common web attack method. Attackers inject malicious code into commands entered by users to perform illegal operations. In order to effectively defend against command injection attacks, the following are some important defense measures:

1. Input verification and filtering: Strict verification and filtering of commands entered by users to ensure that only legal characters and commands are allowed. You can use a whitelist mechanism to allow only specific commands and parameters to pass verification.

2. Parameterized queries: When executing database queries, use parameterized query statements instead of splicing user-entered commands. Parameterized queries can effectively prevent command injection attacks because parameter values ​​are automatically escaped and will not be executed as commands.

3. The principle of least privilege: When configuring the execution environment of a web application, ensure that the application has only the minimum privileges. In this way, even if the attacker successfully injects malicious code, he can only perform restricted operations, reducing the impact of the attack.

4. Log monitoring and analysis: Record and monitor application logs in a timely manner, especially logs related to user input. By analyzing logs, abnormal behaviors and potential command injection attacks can be discovered in time, so that corresponding defensive measures can be taken.

5. Regular updates and maintenance: Timely updates and maintenance of relevant components and frameworks of web applications, including databases, operating systems, and the application itself. By promptly fixing vulnerabilities and updating security patches, the risk of command injection attacks can be effectively reduced.

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The next part is about other common attacks:
In summary, through defensive measures such as input validation and filtering, parameterized query, principle of least privilege, log monitoring and analysis, and regular update and maintenance, the impact of command injection attacks on web applications can be effectively reduced. threaten.