<![CDATA[Phishing Campaign Sends Millions of Emails Using Invisible Unicode to Evade Filters]]>Microsoft is tracking a high-volume phishing campaign that abuses invisible Unicode tag characters to slip past email security filters. The attackers are not using these characters to conceal instructions from human readers while revealing them to AI models — they are using them to fragment financial trigger words like “funding” mid-string, so that automated filters fail to parse the malicious intent of the message.

According to the Microsoft Security Research team, the campaign has already sent out millions of emails, relying on this Unicode-based obfuscation to keep payloads and lure text under the radar of legacy detection systems.

  • The technique involves inserting invisible Unicode tag characters into key financial terms, breaking the literal string.
  • This prevents signature-based and keyword-matching filters from flagging the email as malicious.
  • The campaign volume is described by Microsoft as “high-volume,” indicating broad targeting.

For defenders, the key takeaway is that email security layers relying solely on keyword or regex-based detection are now insufficient. Organizations should prioritize behavior-based analysis, link reputation scoring, and sender authentication checks to catch these obfuscated lures before they reach inboxes.

Source: The Hacker News

Is your email gateway equipped to flag messages with unexpected Unicode characters, or would this kind of obfuscation bypass your current defenses?

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