Create Gmail filter for subject lines containing UTF-8 special characters

Question

Lately I'm receiving a lot of spam that contains animations in the subject lines. Here is an example, from the source of a message, of a subject line containing animating fireworks.

Subject: =?UTF-8?B?876toA==?=Zero APR. No Credit Required. No Spend Limit!=?UTF-8?B?876toA==?=

I'm trying to create a Gmail filter that will automatically delete these kinds of messages with the fireworks in the subject line.

But I can't get this to work. I've tried filtering on subject text such as: =?UTF-8?B?876toA==?= or 876toA==

but this doesn't catch these emails. Does anyone know how I can create a Gmail filter that will successfully match these messages with special UTF-8 characters?

* Update 2015-07-27 * See here for an example of the full message source for one of these spam emails. I've replaced my name and email address with '[redacted]'. https://gist.github.com/anonymous/cfd57dcf6d3e87203295

Answer 1

You can use Google Script to perform exact matches in Gmail.

See: Advanced Gmail Filters with Apps Scripts

function filterGmail() {
  var threads = GmailApp.getInboxThreads();
  for (var t in threads) {
    var subject = threads[t].getFirstMessageSubject();
    if(subject.match(/REGEX HERE/) {
      // DO SOMETHING
    }
  }
}

Answer 2

Filtering spam by matching exact strings in an email has been a losing battle for years. When you add one string to filter, they just switch to using a different string. Services such as Gmail use bayesian filters and machine learning which can adapt to the new tactics spammers use. Instead of trying to filter the UTF-8 string you found in that individual message, report it to Gmail as spam so their adaptive spam filters can learn to flag future messages of that type as spam.

Answer 3

If you don't get any legitimate email with UTF-8 in the subject line, then you could create a filter that catches everything with UTF-8 contained in the subject.

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Here's how: Go to Settings (on the right, near the top), then choose the Filters tab. Scroll to the bottom, and click on "Create a new filter." In the Subject part of the form, type UTF-8. Now click on "Create filter with this search" (bottom right). Check "Skip the Inbox" and "Apply the label". For the label, you could use Trash, or you could create a new label, such as "my-spam." Or if you're very sure none of those messages are worth reading, you could check "Delete it." When you're done checking boxes, click on "Create filter."