According to this article, it takes a lot of tech to whip up a form of anthrax that can be used as a weapon:

In liquid form, anthrax is useless - droplets would fall to the ground, rather than staying suspended in the air to be breathed by victims. Making powder needs repeated washings in huge centrifuges, followed by intensive drying, which requires sealed environments. The technology would cost millions.



US intelligence believes Iraq has the technology and supplies of anthrax suitable for terrorist use. 'They aren't making this stuff in caves in Afghanistan,' the CIA source said. 'This is prima facie evidence of the involvement of a state intelligence agency. Maybe Iran has the capability. But it doesn't look likely politically. That leaves Iraq.'



(boldface mine)

I'm assuming that those samples of anthrax that have been identified to date are undergoing heavy testing and DNA analysis to track the source. I think that within a very short time, someone's fingerprints are going to be found all over this low-key anthrax attack.