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What is Remote File Inclusion (RFI) and how can you prevent it?

Have you ever wondered why some people and organizations pay so much attention to their web applications? They understand that not prioritizing the security of their networks is an invitation for cyber attackers to come in and do damage.

And one of the ways these attackers enter a network is through RFI (Remote File Inclusion) attacks.

RFI attacks are quite common and can be easily performed on targeted websites. You certainly don’t want to be the target of the attack. In this article, you will learn how to prevent it.

What is Remote File Inclusion (RFI)?

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Remote file inclusion is a technique used to operate websites and web applications. It addresses inadequate entry validation vulnerabilities.

With such loopholes, the attacker adds malicious remote files to web pages and applications. This is only possible for web applications that dynamically accept scripts and external files.

RFI attacks are quite dangerous because they can lead to the loss of sensitive information, cross-site scripting, remote code execution, and a complete system replacement.

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RFI attacks result in over 25% of malicious sessions on websites and are more common than other forms of attacks such as cross-site scripting and SQL injections.

The lack of sound cybersecurity practices to improve the security of web applications is one of the main factors responsible for the prevalence of RFI attacks.

How does the inclusion of remote files work?

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A remote file inclusion occurs when a file from a remote web server is added to a web page. This allows the attacker to view the content of a web application.

RFI also occurs when there is a misconfiguration of programming code, leaving a vulnerability that attackers can exploit to enter your system. Web applications written with PHP codes are more vulnerable to RFI attacks than others. PHP includes functions which favor the inclusion of remote files. In the case of other languages, it takes a series of steps to enable such a vulnerability.

Although file inclusion can occur in most web applications, those written in PHP code are more prone to RFI attacks, as PHP has native functions that allow remote files, while other languages ​​require workarounds. workaround to do the same.

To include a remote file, you need to add a string with the URL of the file to an include function if you are using PHP codes. Otherwise, you will need to use the equivalent code in your programming language.

When the code is executed, the web server will request the remote file. After the remote file is included, the web page displays all of the content.

What is the impact of an exploited remote file inclusion?

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The extent of damage caused by a remote file inclusion attack depends on the type of remote file included and the execute permissions granted to the web server user.

If the remote file contains malicious code, the web server will execute these codes with the content of the web page. This allows attackers to steal sensitive information, hijack web servers, and defame web content.

The RFI attack goes beyond immediate web application security for web servers with administrative privileges to trigger a total system failure.

How to Identify Remote File Inclusion Vulnerabilities

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Early detection is an effective defense against cyber threats. Using intrusion detection systems makes a big difference in preventing what could have been a deadly attack. Likewise, detecting the signals of an RFI attack in good time saves you a lot of damage. You have the opportunity to rectify the problem before it gets worse.

Running an automated scan with a vulnerability scanner is effective in identifying remote file inclusion vulnerabilities because it highlights pending threats.

Once the danger is exposed, restrict the inclusion of files based on user input. But this method may be impossible to implement in some cases. You must have an allowed list of files to include.

If you are working with a PHP application, you can allow_url_include enabled in php.ini for recent installations. This setting helps you identify vulnerabilities in your network to build a strong defense.

How to prevent Remote File Inclusion (RFI) vulnerabilities

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Failure to put measures in place to prevent an RFI attack exposes your website to serious consequences. These include loss of website content, degradation and exposure of sensitive data through your web hosting server.

If you want to secure your system against RFI attacks, here’s how.

1. Use filters to clean up input parameters

Allowing your web server to process all user input for HTTP requests increases your vulnerability to RFI attacks. Do not trust any input provided by the HTTP request.

Make sure all requests are properly screened using filters to check for threats. This way, you can intercept malicious requests at the gate before they reach your network.

2. Avoid arbitrary input data

A safe way to prevent an RFI attack is to avoid the use of arbitrary input data in a literal file include request. Allowing such data input permissions from users makes your website more likely to receive a remote file.

Web crawlers and hackers use these input requests to gain unauthorized access to web applications. Instead of allowing any entry, implement strong and effective access control before dealing with user requests.

3. Create a dynamic authorization list

A dynamic whitelist is a user-created file saved with a file name in a record. Whenever the file is needed, the file name can be used for the entries. Since the file name has already been stored in the recording, the web page can easily verify the file before execution.

Websites free from RFI attacks are more difficult to create than others. This is why we have more websites subject to remote file inclusion. But when checking out the risks of leaving your webpage vulnerable to RFI attacks, it is best to build your webpages with a high level of immunity.

Validating and disinfecting inputs can significantly reduce the risk of RFI attacks. You cannot be sure that the entries are completely free from the inclusion of remote files. Therefore, it is necessary to carry out sanitation before execution.

Make sure that the following user-supplied / controlled entries are thoroughly cleaned before execution.

  • Cookie values

  • GET / POST parameters

  • URL parameters

  • HTTP header values

The disinfection process involves checking the input fields with an authorization list. Blocklist validation is hardly used because it is weak and does not scan entries in hexadecimal or encoded formats. This allows attackers to use different formats to provide input files that give room for RFI attacks.

Take charge of your cybersecurity

Inclusion of remote files is an attacker’s strategy to steal or erase sensitive data from your web application. Depending on the attacker’s motive, the attack can be fatal.

Naturally, even the most secure web applications develop vulnerabilities. The difference is in their ability to resolve potential threats before they escalate.

Remote file inclusion vulnerabilities can be an opportunity for you to increase the security of your network if you are on top of your security game.


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