Brazilian attacks are evolving day-by-day, becoming more complex and efficient. It is there necessary to be wary of emails from unknown sources, especially those containing links and attached files.
Since the malicious payload hosted in the PNG file cannot be executed without its launcher, it cannot be used as the main infector; that is usually delivered to your mailbox, so it has to be installed by a different module.
This technique allows the criminals to successfully hide the binary inside a file that appears to be a PNG image. It also makes the analysis process harder for antivirus companies as well as bypassing the automated process to detect malicious files on hosting servers.