There are different and sometimes confusing messages regarding the specific malware used to steal card data from Target stores. Some of them name KAPTOXA as the malware responsible for the attack and reference iSIGHT Partners report. I haven't seen this report so I can't say KAPTOXA directly related to target breach. First time I heard and wrote about KAPTOXA back in May 2013. Interesting fact: the word "KAPTOXA" consist of letters which look the same in both Latin and Cyrillic alphabets, although some of them stand for sounds. If you read this word as Cyrillic letters, it is Russian slang word meaning “potato”.
However, I would rather trust McAfee blog which states that the actual malware is “BlackPOS” which contains string "Rescator" which links it to Russian hackers. It is unclear at this moment whether there is any link between KAPTOXA and BlackPOS.