While most cybercriminals tend to set their sights on siphoning valuable data from poorly protected enterprises, there's no limit to the kinds of targets they'll seek out. There's no honor among thieves, so it shouldn't be a surprise that with the right kind of motivation, malicious hackers will happily attack other black hat and grey hat hackers.
Sometimes the attacks are purely mercenary: rivals know they can hit pay dirt very quickly if they find an easy way to tap into data stores of already vetted stolen identities or financial information. Similarly, certain kinds of cyber skirmishes are initiated to take competitors out. And then there are the attacks that are a little more personal: to show someone up, settle a score, or otherwise make a philosophical stand.
Regardless of the motives, these kind of squabbles offer up a satisfying dose of schadenfreude for cybersecurity pros beleaguered by the bad guys. It's nice to watch them fight amongst themselves every once in a while. So, pull up a chair, grab some popcorn and read on.