Once popular for attacking AI, ASCII smuggling is embraced by spammers
Spammers adopt ASCII smuggling—invisible Unicode tag characters—to evade email filters, with Microsoft Defender detections spiking to 2.5 million per day.
ASCII smuggling hides text in Unicode tag characters (e.g., U+E0041 for "A") that are invisible to humans but readable by LLMs and text processors. The technique gained attention as a stealthy prompt-injection vector and is now used by spammers to obfuscate keywords from email detectors. Microsoft reported Defender for Office smuggling detections jumped from roughly 21,000 per day to over 1.3 million in early February, reaching 2.5 million within four days, before falling sharply in mid-May.
- Unicode tag characters encode ASCII-like text invisible to human readers
- Defender for Office detections rose from ~21,000/day to 2.5 million within days
- Same property enabling prompt injections now defeats spam filter keyword checks
- Campaign volume persisted for months, then dropped sharply in mid-May
- Vendors
- Microsoft
- Products
- Microsoft Defender for Office
From the original article
1 min read at arstechnica.com
A once-overlooked block of unicode that's invisible to humans is gaining ever wider use.
By Dan Goodin · arstechnica.com
A short excerpt; the article and its images belong to the publisher. Summary, key facts and assessment above are AI-written from the article and can be wrong.