What is Spam Filtering?

Spam filters detect unsolicited, unwanted, and virus-infested email (called spam) and stop it from getting into email inboxes. Internet Service Providers (ISPs) use spam filters to make sure they aren’t distributing spam. Small- to medium- sized businesses (SMBs) also use spam filters to protect their employees and networks.

Spam filters are applied to both inbound email (email entering the network) and outbound email (email leaving the network). ISPs use both methods to protect their customers. SMBs typically focus on inbound filters.

There are many spam filtering solutions available. They can be hosted in the “cloud,” on computer servers, or integrated into email software such as Microsoft Outlook.

How do spam filters work?

Spam filters use “heuristics” methods, which means that each email message is subjected to thousands of predefined rules (algorithms). Each rule assigns a numerical score to the probability of the message being spam, and if the score passes a certain threshold the email is flagged as spam and blocked from going further.

There are different types of spam filters for different criteria:

  • Content filters – parse the content of messages, scanning for words that are commonly used in spam emails.
  • Header filters – examine the email header source to look for suspicious information (such as spammer email addresses).
  • Blacklist filters – stop emails that come from a blacklist of suspicious IP addresses. Some filters go further and check the IP reputation of the IP address.
  • Rules-based filters – apply customized rules designed by the organization to exclude emails from specific senders, or emails containing specific words in their subject line or body.

You can also run your message through certain tools, such as Mail Tester to test the ‘spammyness’ of an email.

No single method is a complete solution to the spam problem, and there are always trade-offs (which the heuristics try to weigh) between rejecting legitimate email vs. letting spam slip through.

Is spam filtering necessary?

In today’s world, spam filtering is a must to protect your business. Spam is not going away.

It is estimated that 70 percent of all email sent globally is spam, and the volume of spam continues to grow because spam remains a lucrative business. Spammers get ever more sophisticated and creative in their tactics to get their messages into your inboxes and wreak their havoc. Spam filtering solutions must continually be updated to address this evolving threat.

Why is spam filtering important?

A spam filtering solution cannot be 100 percent effective. However, a business email system without spam filtering is highly vulnerable, if not unusable. It is important to stop as much spam as you can, to protect your network from the many possible risks: viruses, phishing attacks, compromised web links and other malicious content.

Spam filters also protect your servers from being overloaded with non-essential emails, and the worse problem of being infected with spam software that may turn them into spam servers themselves.

By preventing spam email from reaching your employees’ mailboxes, spam filters give an additional layer of protection to your users, your network, and your business.

Do you need a spam filter?

At the very least, spam email is a nuisance that will clog up your employees’ inboxes and overload your servers. Spam is also dangerous — the entry point for serious attacks that could damage your computers, your computer network, your bottom line, and even your company’s reputation. Yes, you need a spam filter solution as the key first line of defense.

How can spam filters help you?

We hope you are convinced that spam filters are essential to protect your business. When you decide to invest or upgrade your spam filter solution, know that there are countless spam filter programs out there and it will take time to figure out which one works best for your business.

Here are a few key things to look for:

  • At a minimum, the solution you choose must block spam. This might sound like a given, but not all spam filter software is up to the job (or doesn’t keep up to date with the evolving world of spam attacks).
  • The solution you choose must provide the security you need for your network, but not stop the legitimate emails your employees need to conduct their business.
  • Administrators must have the ability to edit and create rules over and above predefined rule settings so that the solution meets your organizational needs. This customization should be easy, even for unsophisticated computer users.

 

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