As new methods are introduced, spammers find ways around them. This is how the most effective software works. The first method is called blacklist. The blacklist works by identifying the IP address of the sender's computer, then blocks communication with this IP. The second method is filtering. Bayesian filtering is the most popular filtering method. It works by analyzing the mail you read and the mail you don't. It is therefore able to learn over time which mail you want and which you don't. The third method is called profiling. This analyzes the message for telltale signs of spam such as pattern, keywords, invalid message IDs, and bugs. The message is then assigned a score. If the score exceeds a certain threshold the message is discarded. The last method is simply called labeling. In most states, senders are required to mark their messages as spam or legitimate mail. This allows the user to choose whether they want to see or not