Ask HN: Un-filterable new type of SPAMs in Gmail

I am recently receiving new type of spam in my gmail inbox that I am not able to filter. The particularity is in the file attached which is an .html (body is often empty, random email and from as always). Spam is lending in my main inbox, and would like to simple filter all email containing html files. But we can't add a custom filter on filename, can we ?

We can indeed filter on filename : "filename:html"