Let’s Decrypt Extensions

Everything beyond the period (dot) in a file name is the file extension. File extensions are a way to identify the type and format of a file. Below are some key points to know about file extensions. Familiarize yourself with common file extensions along with their meanings and functions to enhance your digital literacy and cybersecurity.

File Extension Information

File Type Identification: File extensions typically consist of a period (dot) followed by a few letters or numbers at the end of a file name (e.g., “document.docx”). They help both users and operating systems identify the type of file and associate it with the appropriate program for opening or handling.

Associated Programs: Each file extension is associated with specific programs that can open or interpret files of that type. Format Information: File extensions often provide information about the format of the file such as .jpg, .PDF or .mp3.

Compatibility: File extensions are important for compatibility. Some programs may only recognize or open certain file types, and using the correct extension ensures proper handling.

File Compression: File extensions can also indicate whether a file is compressed such as .zip and .rar extensions.

Web Development: In web development, file extensions like .html and .css are crucial. They indicate the type of content and how it should be interpreted by web browsers.

Security Considerations: Be cautious about file extensions in email attachments or downloads. Some malicious files may have deceptive extensions (e.g., .exe files disguised as .pdf).

Changed Extensions: Changing a file extension doesn’t change the file format or actual file content. For example, renaming a .txt file to .jpg doesn’t convert the text content to an image.

Hidden Extensions: Some operating systems may hide file extensions by default. It’s a good practice to enable the display of file extensions to avoid confusion with similarly-named files.

photo by Mark M. Hancock / © The Beaumont Enterprise

File Extension Programs and Functions

Below are examples of the countless file extensions. Each is associated with specific programs and functions. .txt means text. It’s associated with plain text editors and files.

.doc, .docx means document. It is associated with Microsoft Word and Google Docs. Its function is word processing. 

.xls, .xlsx is associated with Microsoft Excel and Google Sheets. Its function is spreadsheets often with specific formulas. 

.ppt, .pptx is associated with Microsoft PowerPoint and Google Slides. Its function is presentation files.

.pdf means Portable Document Format. It is associated with Adobe Acrobat and various PDF readers. It helps documents that should look the same on any device.

.jpg, .jpeg means Joint Photographic Experts Group. It is associated with image viewers and Adobe Photoshop. Its function is to compress, view and share digital images.

.png means Portable Network Graphics. It is associated with image viewers and Adobe Photoshop. It is commonly used for web graphics. .gif means Graphics Interchange Format. It is associated with web browsers and image viewers. It is often used for simple animations. 

.mp3 is associated with media players. Its function is to create and store compressed audio file formats.

.mp4 is associated with video players and video editing software. Its function is to create and store compressed video file formats. 

.html means Hypertext Markup Language. It is associated with web browsers and text editors used to create web pages.

.css means Cascading Style Sheets. It is associated with web browsers and text editors. It is used to style HTML documents.

.exe means executable file. It is associated with Windows or any other executable software. Its function is to launch a program or installer.

.zip is associated with WinZip and 7-Zip compression tools. It functions along with a compressed archive file.

Beware of Hackers

Practice good cybersecurity hygiene and be cautious when handling files from untrusted sources. Use reputable antivirus software, keep your operating system and software up to date, and be wary of unexpected or unsolicited email attachments - especially if they come from unknown sources.

Hackers often employ tactics to disguise malicious files and payloads. A specific file extension doesn’t automatically make a file malicious. However, some extensions are more commonly associated with potentially harmful content used by attackers: .exe (executable files), .vbs (Visual Basic Scripting code), .js (JavaScript), .bat (Batch), .ps1 (PowerShell), .dll (Dynamic Link Library), .scr (Screen Saver), .zip or .rar (compressed archives), .html (HTML), and macro-enabled documents such as .docm, .xlsm, .pptm. Malicious macros are used in phishing campaigns.

I’ve Got Your Six!

Mark M. Hancock, GRI, MRP, AHWD
REALTOR, New Build certified
214-862-7212
DFWmark.com

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