Definition and Methods of Spam Filtering and How a Spam Filter Works

Spam filtering is a procedure that identifies dangerous incoming messages from attackers or vendors. Attackers often use emails claiming to offer a helpful service or protect you from imminent danger.

Yet, they are just clickbait, designed to get you to click on a link that downloads malware to your computer or sends you to a dangerous location.

Spam Filter

Email spam filters are virtual walls that block unwanted, malicious code that contains unwanted and transmissible virus emails from achieving the user’s inbox. It is a software application that defends users from spam. 

Dozens of billions of spam emails are circulated daily. That’s almost 50 percent of the world’s regular email traffic. Internet Service Providers (ISPs) utilize spam filtering methods to ensure that they do not send corrupt incoming emails or links to the recipient.

How Do Spam Filters Work?

Spam filters use practical methods, which means that every email is subject to thousands of predefined rules (algorithms). Each rule assigns a numerical rating to the likelihood that the message is spam, and if the result crosses a certain threshold, the email is marked as spam and is blocked from going any further.

There are multiple spam filtering solutions and the best spam filter for you and your business to secure future emails – to avoid any spam message from legitimate emails. Spam filters exist as gateway spam filters and therefore, spam software needs to be activated.

Types of Spam Filtering

There are multiple types of spam filters.

User-defined Filters

User-defined filters are included in most email services and work by forwarding emails to different mailboxes depending on the headers or content. You may already be using them to organize your inbox, with set rules for sending messages from certain friends to specific subfolders.

In the same way, emails are identified as unnecessary and filtered if the origin or content is suspicious. For these practices to function, the filter needs to create a database of typical spam email features, which will prompt you to decide if email-specific sources or specific content are unwanted.

A reasonably small number of user-defined rules can significantly eliminate several more advanced spam email filters since they value email for information stored in the recipient, sender, and subject fields displayed by mail browsers.

Header Filters

Header filters scrutinize the information left by the servers used to deliver your email, known as a relay chain. Spammers do not want to be tracked and put false information in the relay chain to prevent people from responding to emails that follow their location.

Header filters filter spam folders to detect fake headers that are a sure sign of email.

Language Filters

Language filters filter the email, not the recipient’s language. They are of limited usage unless your default language is English due to the widespread use of English online.

In recent years, sophisticated content filters have further improved the efficiency of spam filtering.

Spam Filtering Methods

Spam emails are sent every day long. In such an event, spam can interrupt your busy days, forcing you to spend time opening and deleting herbal remedies or once-in-a-lifetime investment opportunities. Spam can unleash a nasty virus on your organization’s network in a more severe scenario, crippling your servers and desktops.

Desktop spam filters block messages from specific senders to improve email deliverability.

Anti-spam applications typically use one or more filtering methods to identify spam and prevent it from reaching the user’s inbox. But just because anti-spam programs are designed to do the same thing does not mean that they all work the same way.

At this time, let’s take a closer look at the proven methods to filter spam …

Methods of Spam Filtering

Researching Spam-filtering Products

Now that you know how to use different anti-spam methods to stop junk email, you will be reasonably organized when it comes time to research the many products on the market.

Challenge/Response System

Spam filters that employ a challenge and/or response system block unwanted emails by forcing the sender to complete a task before delivering his message.

For example, send an email to someone using a challenge/response filter. You will likely receive an email immediately asking you to visit a webpage and enter the code displayed there on the form.

Blacklist

This popular spam filtering method stops unwanted emails by blocking messages from a preset mailing list that you or your organization’s system administrator assembles. Spam filters work as inbound filters

Blacklists are forms of email addresses or Internet Protocol (IP) addresses that were earlier used to send spam. When an incoming message emerges, the spam filter inspects if its IP or email address is blacklisted; if so, the message is considered spam and is rejected.

Whitelist

The whitelist blocks spam using a system almost opposite to the blacklist. Instead of letting you specify which senders to block mail from, the whitelist enables you to identify which senders to intercept mail from; these addresses are listed as trusted users.

Greylist

A relatively new spam filtering technique, civilists use the fact that many spammers try to send a series of junk mail only once.

Bayesian Filters

The Bayesian filter is considered one of the most advanced forms of content-based filtering, employing mathematical probability laws to determine which messages are legitimate and spam.

Collaborative Filters

Collaborative content filtering takes a community-based approach to fight spam by collecting data from millions of email users worldwide.

DNS Lookup Systems

Although not an extremely secure method in itself, several anti-spam ways use the Domain Name System (DNS), which all Internet mail servers use to identify themselves to identify and disable spammers.

List-Based Filters

List-based filters stop spam by categorizing senders as spammers or trusted users and properly blocking or allowing their messages.

Real-Time Blackhole List

This method of filtering spam works almost identically to the traditional blacklist but requires less practical maintenance. It is because most real-time blacklists are maintained by third parties, who take the time to build comprehensive blacklists on behalf of their subscribers.

Content-Based Filters

Instead of applying general policies to all emails from a particular email or IP address, content-based filters evaluate the words or phrases in each message to determine if the email is spam or valid.

Word-Based Filters

A word-based spam filter is the simplest type of content-based filter. Generally, word-based filters block any email that contains specific terms.

Conclusion

Although many spammers are relatively harmless, email providers use spam filtering to make their users’ experiences as offensive as possible. Spam can fill your inbox to the point where the amount of storage available is approaching its limit, and inbox management becomes a pain.

The best spam filtering for your needs will depend on the challenges and goals of your business. When a user migrates from one supplier to another, the home provider will lose money, so if you keep it around trying to eliminate spam, you will improve their bottom line.

In this case, users may have to choose between upgrading their storage or getting another free email account. Spam filtering is definitely a crucial element of the email ecosystem.