What is ASCII smuggling, and how is it helping spammers bypass AI email filters?
ASCII smuggling is an evasion technique used by spammers to bypass AI-powered email spam filters. As AI systems and email filters have become more advanced, spammers have turned to sophisticated methods to get around detection. ASCII smuggling involves inserting invisible Unicode tag characters into email content, which prevents filters from properly processing the text.
These tags are readable by computers but nearly invisible to humans, allowing spammers to hide malicious content without raising suspicion. Microsoft researchers observed a significant increase in ASCII smuggling during a phishing campaign in February 2026, with the number of detected signatures jumping from around 21,000 per day to over 1.3 million in a single day, and up to 2.5 million in the following four days.
To combat this threat, Microsoft suggests that developers update email filters to better detect and handle these invisible Unicode tags, which remain a major challenge in modern email cybersecurity.
Written by urgent.news from The Indian Express's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
