Challenge 17: Sub-64 Size Gate

Difficulty: Medium
Category: Non-Printable Ratio Bypass

Objective

The non-printable ratio check has a minimum file size requirement. Exploit this threshold by crafting functional shellcode or a malicious script that fits below the minimum size, completely evading the ratio check.

Scanner Behavior

The scanner’s non-printable byte ratio check only activates for files that are 64 bytes or larger. Files smaller than 64 bytes skip this check entirely, regardless of how many non-printable bytes they contain.

This is a deliberate design choice — very small files are assumed to be too tiny to contain meaningful threats, and checking them would produce too many false positives on small binary stubs.

Rules

Your file must be less than 64 bytes in total size.
The file must contain non-printable bytes (binary content) that would trigger the ratio check if the file were larger.
The content should be functional — either valid shellcode or a working script that performs some action.
Demonstrate that the scanner’s ratio check does not fire on your file.

Hints

If the file is too small, the check simply doesn’t run. No check means no detection.
What’s the minimum viable shellcode for your target architecture? Some operations can be done in surprisingly few bytes.
Think about what can be accomplished in under 64 bytes of raw machine code or a tiny script.
x86/x64 has some very compact instruction sequences for common operations.

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