File uploads are necessary for any business. You use them for services, applications, and user productivity. File uploads are a fundamental function of Content Management Systems (CMS), insurance sites, messaging applications, and healthcare portals.
However, unrestricted file uploads create an additional attack vector for cyber-criminals. In this article, you will learn about seven crucial file upload security issues, and nine methods for protecting file uploads.
File Upload Security Issues
The following list includes some of the risks when uploading files on your website.
1. Overwriting files
You can unintentionally overwrite an existing file when you upload a new file with the same name and extension.
Attackers can use the new file to launch a server-side attack if the overwritten file was critical. Server-side attacks can bring down a website, or allow attackers to upload more malicious files by changing the security settings of a server.
2. Snooping attacks
Snooping attacks involve an intruder listening to traffic between two machines on a network. Cloud storage is very vulnerable to snooping attacks because the files are stored and transmitted over the Internet.
Hackers can even get their hands on encrypted files in the cloud. Companies must transmit files over a secure connection and ensure that data is always encrypted to prevent outsiders from accessing files stored in the cloud.
3. Uploading very large files
Extremely large files can lead to multiple failures in applications. For example, attackers can execute Denial of Service (DDoS) or botnet attacks that upload many large files simultaneously.
As a result, the system breaks down because it does not have the capacity to execute legitimate operations and large file uploads at the same time.
4. Blacklisting file extensions
The purpose of blacklisting file extensions is to keep track of potentially dangerous extensions. The system verifies that the file extension is not on the blacklist during the file upload.
The file is rejected if it is on the list. Unfortunately, you cannot list all possible extensions in the blacklist. Attackers can use an extension that is not included on the list to mislead the security system.
5. Multipurpose Internet Mail Extensions (MIME) validation
MIME is a standard that extends the limited capabilities of emails by enabling the insertion of images, sounds, and text in a message.
Attackers can bypass MIME type validation security to inspect the content of a specific file. For instance, MIME sniffing is a technique to identify a file format. Hackers can leverage MIME sniffing to implement Cross Site Scripting (XSS) attacks.
6. Malicious content
Uploaded file content can include malware, exploits, and malicious scripts. Attackers
This article was written by Gilad David Maayan and originally published on WP Mayor.