Once popular for attacking AI, ASCII smuggling is embraced by spammers

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A clever technique used to hide malicious prompts in attacks on AI agents has been adopted by spammers to evade filters on email platforms that are designed to flag unwanted messages used in mass campaigns.

The technique is broadly known as ASCII smuggling. It gained attention two years ago as a means of making a class of AI attack known as prompt injections more stealthy. Malicious instructions embedded in emails or other untrusted content to be processed by an LLM aren’t written in ordinary text. Instead, they’re rendered by a special range of Unicode tags. For example, the tag point U+E0041 mirrors “A,” and U+E0061 mirrors “a.”

No longer just for obscuring prompt injections

The block of 128 tags mimics a portion of the American Standard Code for Information Interchangealmost perfectly, with one major difference: the characters they encode are readable by computers but, by design, are almost completely...

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