Millions of spam emails are sent to people every day, and some companies exist solely to help the people that send these annoying additions to you inbox. The good news is that there are other companies working hard every day to combat these unwanted intrusions. There is a lot at stake, as not only does it take time to deal with spam emails, they often contain harmful viruses that spread when people click on links. They also often contain scam offers urging people to take advantage of a great sale, or send money in order to receive a lot more money in return. There are several ways that anti spam services combat this problem, from a relatively simple approach to more complex attacks meant to capture even the best hidden spam emails.
Some anti-spam software operates by detecting common words used in spam emails, such as “sex”. Spammers use these words in the subject lines of emails in the hopes of raising people’s curiosity so they open the mail. The problem with this simple approach is that people who are sending the harmful emails can change the way words are spelled, or add dashes between letters in order to avoid detection. These simple filters may also filter out mail you actually wanted to receive based on the existence of those key words.
Bayesian and heuristic filters take the fight against spam to the next level by identifying entire word patterns counting the frequency of certain key words. Because they rely on statistical models specifically aimed at recognizing spam, these filters are better able to identify spammers that sidestep the simpler spam filters.