How Does A Spam Filter Work?
How does a spam filter work? Spam filters use either text filters, or eliminate messages based on the sender and their history. The majority of top spam filters use both of these tools to make sure that as little junk ends up in the mailbox as possible.
Text filters work by using algorithms to detect which words and phrases are most often used in spam emails. Phrases like “male enhancement”, “vicodin”, and “online pharmacy” are often an immediate flag for removal by filters. Spammers have gotten wise to this, and often use blatant misspellings or even substitute characters (v1cadin for s4le) in order to make it past the filters. Fortunately, modern spam filters also make allowances for these types of misspellings and if a word comes up, even with character substitutions, the message will still be blocked.
In addition to simple text filter algorithms, the top spam filters use client identity and history to block malicious or annoying spam e-mails. How does a spam filter work? This is done by looking at all of the messages a certain user has sent out. If they send out huge amounts of emails constantly, or if several of their messages have already been marked as spam through the text filters, their emails will often be blocked entirely.
Spammers vs the Filters
As previously discussed, spammers are always trying to win the war against spam filters. How does a spam filter work? By taking these measures that spammers use such as character substitution and making them obsolete by doing a more heuristic approach of spam detection, both through text filters and by malignant client detection.