StrangeBrew virus does not create new .class files, it searches for existing .class files and modifies them to include a copy of itself. When the "infected" .class file is executed, the virus gets control and then passes control to the original code in the file.
When run, StrangeBrew searches the current directory for .class files. It includes it's own code into the host .class files and modifies them to start the execution from the virus part. Virus adds call to it's own code as the first line of host constuctor or main method. The infector routine in StrangeBrew is rather buggy, and most of the time doesn't infect host corretly, breaking the host.
Being Java based virus the StrangeBrew is capable of executing in almost any platform that has Java runtime environment installed. The virus is capable of executing on Windows and Linux platforms and in PDA devices which have Java runtime installed.
StrangeBrew does not do anything else except spread. As such, it can not be considered a realistic threat. It has not been found in the wild.