Posted 1 December 2017 in Blog News

Spamfilter Goldilocks – too hot, too cold or just right?

Image courtesy of Stuart Miles at

Spam filters are an essential cyber security tool, greatly reducing the likelihood of e-mails carrying viruses and other malware from reaching user mailboxes. They have the added bonus of removing the dull job of deleting dozens of unwanted, unsolicited messages.
Spam filters have fairly sophisticated methods of weeding out junk messages: checking the header information, checking the sender address against blacklists of known spam senders, looking for common spam keywords in the content or the subject line, using algorithms based on known spam to identify likely spam messages. These blacklists and algorithms improve every time you mark a message as spam, so this little gesture benefits everybody. Spam filters can even often identify deliberate attempts to mislead the recipient by slightly altering or misspelling well-known domain names.

Unfortunately, no spam filter gets it right all the time. Spam senders put some time and effort into trying to make their messages appear innocuous. Very occasionally, a dubious e-mail will manage to slip through, but, more commonly a problem for users, occasionally a legitimate e-mail will be blocked. Users often express frustration that a perfectly innocent e-mail from a potential customer or valued client has been trapped by the spam filter and missed by them.
Spam filters come in varying degrees of sensitivity, and with customisable settings to make them more or less thorough with what they weed out, according to your preference. Generally though, we would always advise erring on the side of caution. Most spam filters give you the option of having a ‘digest report’ message delivered to your inbox every day, or several times a day, which shows you what has been trapped and gives you the option of releasing the message and ‘whitelisting’ the sender, so that their messages don’t get trapped in the future. Better to get users to make the effort to check their digest reports every day than have potentially virus-loaded e-mails landing in their inboxes.
Importantly though, spam filters do not take away the importance of training users in how to spot a suspicious e-mail. Unfortunately, cyber breaches sometimes happen when an unwitting user releases and opens an e-mail that the spam filter has correctly blocked, because it looked convincing enough to fool them. User awareness is a vital part of cyber security that should never be overlooked, regardless of how reliable your technical cyber security systems are.

If you would like to know more about optimising your spam filter, get in touch.

Image courtesy of Stuart Miles at