The mtools package for Linux was just the thing needed. However, compiling it on Mac OS X proved to be a challenge. I downloaded the latest mtools-4.0.11 which fixed a problem in calculating the FAT size. These days, GNU's not what it used to be. There's hardly any documentation for mtools to help. Running make left me with an error stating "Undefined symbols: _iconv...". I managed to compile successfully using the following command:
./configure LIBS=-liconv
After that, cleaning the malware files was a breeze using mattrib, mdel and mdeltree.