Ask HN: What are these gibberish ads?

These gibberish ads are following me everywhere. They are blocks of text (not images) consisting of what look like high-bit ASCII, and they fill the entire allotted banner space:

ÜWƒ©Ö/ÌR½bÍ... etc

Has anyone else been seeing these? Are these a broken ad from an ad server, or some kind of weird NSA protest perhaps?