# Microsoft reports spike in Unicode-tag spam obfuscation

_Friday, September 4, 2026 at 1:18 PM EDT · Security · Latest · Tier 2 — Notable_

![Microsoft reports spike in Unicode-tag spam obfuscation — Primary](https://cdn.arstechnica.net/wp-content/uploads/2026/09/no-eyes-1152x648.jpg)

Microsoft reported a sharp rise this year in spam using invisible Unicode tag characters to obscure keywords from email filters.

Its Defender for Office signatures rose from about 21,000 a day to more than 1.3 million on one day in early February, then reached 2.5 million within four days. The activity persisted for months before falling sharply in mid-May. The technique, known as ASCII smuggling, had previously drawn attention for hiding prompt-injection instructions from people while leaving them readable to language models.

## Sources

- [Ars Technica](https://arstechnica.com/security/2026/09/once-popular-for-attacking-ai-ascii-smuggling-is-embraced-by-spammers/)

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Retrieved: 2026-09-04T22:36:25.335Z
Publisher: Tech & Business (techandbusiness.org)