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Image GenerationAI Safety & AlignmentHacker NewsPublished: Jul 22, 2026, 01:01 JST

Cloak: Free Tool Adds Invisible Noise to Block AI Training

Cloak: Free Tool Adds Invisible Noise to Block AI Training

3 Key Points

  1. What happened

    Cloak, a free web tool created by Timothy via Claude Code, layers invisible noise onto images to make AI models classify them as watermarks or harmful content and refuse to train on them. The tool uses a technique called L-infinity perturbations and projected gradient ascent to maximize cosine similarity scores between a CLIP embedding and a target embedding, steering models away from the protected image.

  2. Why it matters

    Artists face ongoing threats from automated image scrapers that feed training datasets for AI models. Cloak addresses a gap that other protection tools do not fill: it works against mass-scraping pipelines without assuming the image will be used for training (unlike Glaze) or requiring large-scale dataset representation (unlike Nightshade). The protection remains effective even if the image is cropped or resized, offering a practical layer of defense without visible artifacts at default strength.

  3. What to watch

    Cloak is free with limits: maximum file size 30 megabytes, maximum image length 10,000 pixels, 300 processing passes maximum, and 60 images per hour. Best target prompts include 'watermark', 'blood', 'blurry', 'bad quality', and 'explicit content'—labels scrapers routinely filter out. The creator recommends using Cloak alongside Glaze and Nightshade for maximum protection.

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Context & Analysis

Image-scraping pipelines that feed AI training datasets routinely use automated vision models to filter and sort collected images, discarding those flagged as watermarks or containing harmful content. Cloak exploits this filtering behavior by adding imperceptible noise that causes the scraper's own model to classify an image as watermarked or harmful, causing the pipeline to skip it—a defensive inversion of the scraper's own automation.

The tool addresses a real gap in the artist protection landscape. Glaze assumes images will eventually be used for training, which many artists find uncomfortable. Nightshade requires protected images to make up a substantial fraction of a dataset, which is not guaranteed. Cloak instead targets the bottleneck of initial scraping and filtering, making it a complementary rather than competitive approach. The creator's transparent recommendation to use all three tools together, rather than promoting Cloak as a standalone solution, suggests a focus on practical defense depth over market positioning.

However, Cloak's limitations are explicit: it cannot recover images already accepted into training datasets, does not guarantee every model and pipeline will respond to the noise signal, and protection may weaken as models change over time. The tool is positioned as one layer of a multi-part defense strategy that should include copyright registration, metadata embedding, C2PA credentials, and visible watermarks.

FAQ
How does Cloak protect images without making them look different?
Cloak adds faint, carefully-shaped layers of noise that steer an AI vision model's reading toward labels like 'watermark' or 'blood'—categories that image-scraping pipelines routinely discard—without changing how the image appears to humans. At default protection strength (0.008), the noise remains invisible.
What are the limits and costs?
Cloak is 100% free with no ads or data collection. Limits include a maximum file size of 30 megabytes, maximum image length of 10,000 pixels, 300 processing passes maximum, and 60 images per hour. Images are deleted after processing completes.
How does Cloak compare to other AI protection tools?
Cloak fills a niche other solutions do not: it does not assume your image will be trained upon (unlike Glaze) and does not require protected images to represent a large portion of the training dataset (unlike Nightshade). The creator recommends using Cloak, Glaze, and Nightshade together for maximum protection.

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