Like its Linux-based predecessors, Tsunami works by communicating via Internet Relay Chat, or IRC. The malware listens to a hardcoded list of IRC channels on specific servers, and responds to specific commands entered by others in those chatrooms. When triggered, infected computers can be instructed to attack individual websites, by sending large numbers of simultaneous requests. This is known as a Distributed Denial of Service attack (or a live Apple event); the huge number of simultaneous requests to a single website can cause it to crash or go offline.
Even worse, ESET says that Tsunami can force your computer to download additional malware or other software. The company also says that its antivirus software, ESET Cybersecurity for Mac, can detect and remove the malware.