What Are Common File Types You Need to Know?

In cybersecurity, recognizing file types by their extensions is crucial. It helps you quickly determine whether a file is expected, suspicious, or potentially malicious. This can also be helpful when competing in capture the flag (CTF) competitions.

Below is a breakdown of notable file types every cybersecurity professional or beginner should be familiar with, grouped by category for easier reference.

Document File Types

.pdf - Portable Document Format

.doc/.docx - Microsoft Word document

.xls/.xlsx - Microsoft Excel spreadsheet

.ppt/.pptx - PowerPoint presentation

.txt - Plain text file

.rtf - Rich Text Format

Audio File Types

.mp3 - Compressed audio format

.wav - Uncompressed audio format

.flac - Lossless audio compression

.m4a - Audio-only format from MPEG-4

Video File Types

.mp4 - Common video format

.avi - Audio Video Interleave

.mov - Apple QuickTime Movie

.mkv - Matroska Video

Image File Types

.jpeg/.jpg - Common compressed image format

.png - Lossless image compression

.gif - Animated or static image format

.bmp - Bitmap image

.svg - Scalable vector graphics

Executable/Script File Types

.exe - Windows executable

.bat - Windows batch script

.sh - Shell script (Linux/macOS)

.py - Python script

.js - JavaScript file

.jar - Java archive

.vbs - Visual Basic script

Archive and Compressed File Types

.zip - Compressed archive

.rar - Roshal archive (WinRAR)

.7z - 7-Zip archive

.tar - Linux/Unix archive

.gz - Gzip compression

Hash and Security File Types

.md5 - MD5 hash signature file

.sha256 - SHA-256 hash signature

.sig/.asc - Digital signature (e.g., PGP/GPG)

.pcap - Packet capture data (used in network analysis)

Network and System File Types

.tor - Associated with Tor network routing

.log - Log file

.ini/.conf - Configuration file

.dll - Dynamic-link library (Windows system file)

.sys - Windows system file

Final Thoughts

Recognizing file extensions is a foundational security skill. Knowing what a file should be helps you spot when something’s off. This can help prevent malware infections, detect phishing attempts, and identify network threats faster.

Want to test your skills? Check out:

What Are CTFs and Why Should You Do Them?

VirusTotal: Free Tool to Analyze Suspicious Files