Inbox filters, largely successful in protecting email inboxes from incoming mail with inappropriate content, are now facing a new challenge: cleverly worded emails that intentionally misspell such words as penus, brest, and hornni.

Tom Ridge, the Secretary of the Department of Homeland Security, first noticed this breach in the nation’s system of inbox protectors earlier this week when he received an email bearing the subject line, TOMRIDGE, MAKE YOUR PENUS AS LONG AS A GARDEN HOSE!!!

“My first reaction was, what the heck is a penus?” Mr. Ridge said at a press briefing today. “Then when I realized, I said, Holy Toledo, we’ve got a problem here.”...