How Does Spam Filtering Work and How Does It Help?

If half of your inbox is filled with unwanted messages, advertisements and promotional mails, wouldn’t you be frustrated? You would most certainly be, isn’t it? You’d be surprised to know that more than 50% of the mails exchanged everyday all over the world is spam. Constantly receiving spam messages on your work email can be more frustrating as business organizations mostly use emails for all their communication.

Spam is a major issue in business organizations as they flood inboxes with useless messages bringing the overall productivity of employees. Spam messages also consume a lot of resources from email servers and contribute to server outage, memory shortage and power outages. On top of that spam mails even pose security threats as few of them are not junk mails but malicious mails with infiltrate your computer systems for malicious intent. Spam filtering is the most effective counter to these unwanted messages and in this article we will discuss everything you need to know about spam filters.

What is Spam Filtering? How Does it Work?

Email filtering is the most effective way to keep spam at bay and the filtering is quite literally done with the help of many filters. Before sending/receiving mails from a mail server, all the mails are sent through a mail exchange record which is equipped with multiple filters designed to detect spam messages and blacklist the source of the message. These filters are technically advanced, constantly updated and have a specific way of identifying and filtering spam messages. The mail exchange record includes all of these different filters to offer a comprehensive spam filtering service.

Types of Spam Filters

Few of the most commonly used email filter types are discussed below:

1.  List Based Filters

These spam filters identify and block spam messages by tracing the source of these mails and maintaining a blacklist of these sources. This way, all the messages coming from the blacklisted sources will always be blocked. Blacklist filters, real-time blackhole lists, whitelist and gray lists are the most popular list based spam filtering techniques. Similar to blacklist filters, whitelist filters maintain a list of the credible sources and only allow mails from these sources. Real-time blackhole filters are similar to blacklist filters but operate without much human intervention.

2.  Content Based Filters

While the above mentioned spam filtering technique blocks spam by tracing the message source, this technique analyzes the message content to classify a mail as spam or otherwise. There are different types of content based spam filters namely word-based filters, heuristic filters and Bayesian filters. While word based filters look for specific spam words to filters, heuristic filters take multiple words/terms before classifying something as spam.

3.  Other Filters

Apart from content based and list based filters, there are many other effective spam filtering methods. A challenge response system is one of them where the message sender has to perform a task before the mail is delivered. Collaborative filter is another effective technique where inputs from millions of email users are collected to design the particular spam filter.