Phishing Campaign Sends Millions of Emails Using Invisible Unicode to Evade Filters
Microsoft warns of a high-volume phishing campaign using invisible Unicode characters to split keywords like 'funding' and evade filters, peaking at 2.37 million daily messages.
Microsoft's Security Research team documented a high-volume phishing operation inserting deprecated Unicode Tags characters (U+E0000-U+E007F) inside financial keywords such as 'funding' so literal-string and regex email filters stop matching them. The campaign ran on a weekly cadence with 1-2.37 million weekday messages between February and May 15, 2026, peaking on February 26, 2026. It used hundreds of disposable finance-themed sender domains and relayed mail through ActiveCampaign's click-tracking infrastructure (acemlnd[.]com, activehosted[.]com), lending legitimate platform reputation. Microsoft ties the activity to an AI-assisted SBA loan phishing campaign that Fortra's FIRE team disclosed in September 2025.