To most of us, spam is just annoying. However, it can lead to results as dire as identity theft and cyberterrorismj. That makes fighting spam an important task. Here’s an overview of the techniques used to identify and combat unwanted electronic messages.
Some anti-spam actions require human action; others can be automated. Some are integrated in programs. Some can be automated by email administrators or commercial senders. Others are used by those who study and fight spam professionally. The big trade off in spam fighting comes in terms of false positives–identifying legitmate emails as spam. Many types of action try to mitigate this trade off; here are some fo the most common.
Extensive blacklists and greylists are maintainted by mail administrators. A technique called spamtrapping involves putting email addresses where only spammers will find them, and then blacklisting all responses. One of the coolest methods around is statistical content filtering. Statistical content filters take into account what legitimate content usually looks like for a particular user, and makes use of that information to identify which messages are spam. Rule based filtering, which filters messages that meet or fail to meet some set criteria, is more common, and much easier to program. Other tactics involve more levels of user authentification before allowing someone access to email, or more rigorous authentification of website owners using reverse DNS lookups.
Another one of the biggest problems in the spam fight is that spam is highly profitable. Sending spam is basically free, so if any of the targets fall for the scam or buy the product, money has been made. There are various approaches to making it less profitable; attaching even a tiny fee to email would make spam a far less appealing prospect. Alternatively, hefty fines imposed in court could have a substantial deterrent effect, and would not be disproportionate to the resources laid to waist by the work of spammers. Some recent topics are launched on online colleges courses for Anti-Spam Techniques.