"Кракозябра" is a more common spelling, means any strange character. The plural "кракозябры" often refers to a text interpreted in a wrong character encoding.
... which is just a funny, made-up word. Spelling varies, I heard the "krakozyabra" version the most.
I believe "krakozyabra" is used for the symbols in incorrect encoding. The only word that I ever heard for "at" is "собака" (pronounced as suh-buh-kuh)