How to Defend Your Website with Zip Bombs

This article explores the use of zip bombs as a defensive mechanism against automated website vulnerability scanners. While not a foolproof solution, it can deter less sophisticated attacks.

Website administrators frequently encounter malicious activity, including scanning attempts. The author recounts personal experiences with such intrusions, highlighting the sheer volume of log entries documenting these attempts.

The widespread use of WordPress contributes to the prevalence of vulnerability scans targeting common misconfigurations or unpatched plugins. This creates a need for effective countermeasures.

The article introduces zip bombs, leveraging the high compression ratio achievable with repetitive data. A 4.5 petabyte file, for example, can be compressed to just 42 bytes. Decompression attempts consume significant system resources, potentially causing crashes.

The author demonstrates how to create a 10GB gzip file (a format web servers understand) filled with zeros:

dd if=/dev/zero bs=1M count=10240 | gzip > 10G.gzip

A PHP script is then presented to serve this file upon detection of suspicious activity (e.g., known scanner user agents or requests for vulnerable subfolders):

<?php
// ... (PHP code to detect suspicious activity and serve the 10G.gzip file) ...
?>

The script's effectiveness is tested against various clients, demonstrating resource consumption and potential crashes. The results are summarized in a table.

The article concludes with a FAQ section addressing common questions about zip bombs, their impact, detection, and legal ramifications. It emphasizes that while this technique is not a complete solution, it can provide a layer of defense against unsophisticated attacks. The author encourages experimentation (at your own risk).

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