The botnet assembled by the Flashback Trojan that s been infecting Macs is turning out to be a rather difficult one to pin down. Researchers have said that the network of compromised machines may be upwards of 600,000. And now some researchers are questioning whether the entire botnet is made up of Macs or whether there are some Windows machines in the mix as well. Kaspersky researchers are continuing to investigate the question of whether all of the infected machines are Macs.
Source: https://threatpost.com/questions-abound-size-and-makeup-flashback-botnet-040612/76412/