What Is zipinfo?
zipinfo is a command-line utility used to display detailed information about the contents of ZIP archives without extracting them.
In CTF challenges, ZIP files often hide flags or contain password-protected content. zipinfo allows you to quickly inspect:
- File names and directory structure
- File sizes and compression methods
- Modification dates
- Encrypted files
It’s a quick first step to understand what’s inside a ZIP archive before attempting extraction.
Basic Usage
zipinfo file.zip
Example output:
-rw-r--r-- 2.0 unx 1234 tx defN 20-Nov-2025 10:00 file1.txt -rw-r--r-- 2.0 unx 987 tx defN 20-Nov-2025 10:01 file2.txt -rw-r--r-- 2.0 unx 4321 tx defN 20-Nov-2025 10:02 secret_flag.txt
Common Flags for zipinfo
-v→ verbose output (more details, e.g., compression ratio)-l→ list files in a simple format-T→ show timestamps
How zipinfo Is Used in CTF Challenges
1. Listing Contents Without Extracting
Check what’s inside the ZIP without modifying the archive:
zipinfo challenge.zip
- Look for suspicious filenames like
flag.txt,secret.txt, or hidden folders - Check for unusual file extensions or double extensions (
flag.txt.pdf)
2. Detecting Encryption
Encrypted files in ZIPs are common in CTFs:
zipinfoshowsencryptedin the output- Indicates that you need a password to extract
3. Checking File Sizes and Compression
Unusually small or large files may hint at hidden content:
- A 1-byte file could contain a simple flag
- Compressed files may hide steganographic data
4. Exploring Directory Structure
ZIP archives may have nested directories:
- Flags often hidden deep inside
/hidden/or/docs/ zipinfohelps identify where to focus extraction
5. Integration With Other Tools
zipinfo is often used alongside:
unzip -l→ list archive contentsunzip -P <password>→ extract encrypted filesbinwalk→ detect embedded files inside ZIPsstrings→ extract text from individual files
Example workflow:
zipinfo challenge.zip unzip -l challenge.zip strings challenge.zip | grep FLAG
Common Patterns in CTF ZIP Challenges
| Pattern | Description | How zipinfo Helps |
|---|---|---|
| Flag in filename | Flag hidden in file names | Quickly list all files |
| Flag in nested directories | Deeply hidden files | See directory structure without extraction |
| Password-protected ZIP | Requires password to open | Detect encrypted files |
| Compressed flag | Flag inside compressed file | Analyze file size and type |
| Multiple layers | ZIP inside ZIP | Identify archive types and structure |
Recommended Workflow in CTF
- List the ZIP contents with
zipinfo:
zipinfo challenge.zip
- Note suspicious filenames, sizes, or encrypted entries.
- Attempt extraction:
unzip challenge.zip unzip -P <password> challenge.zip
- Use additional analysis tools if needed:
stringsfor textbinwalkfor embedded contentzstegorexiftoolfor images inside the ZIP
zipinfo is a fast, lightweight first step for inspecting ZIP archives in CTF challenges, helping you find flags, detect encryption, and understand the archive structure before extraction.
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