SecureBiz Glossary of Terms

Bayesian filtering

A statistical approach to determining whether an email is spam. Based on probability inference techniques pioneered by English mathematician Thomas Bayes.


A feature of anti-spam software that allows users to designate IP addresses, domain names and individual email addresses from which no mail will be accepted.

False negative

When anti-spam software fails to identify a spam message as spam.

False positive

When anti-spam software wrongly identifies a legitimate message as spam.

Heuristic filtering

Heuristic filtering uses matching rules gained through experience to identify spam. Through detailed analysis of incoming email based on carefully designed rules, heuristic filtering assigns a numerical value or "score" to each message. The score is used to determine whether the message is likely to be spam or not.


All unsolicited commercial email (UCE) and unsolicited bulk email (UBE) that a reipient does not want to receive.


When spammers forge an email address to hide the origin of a spam message. Email scammers and virus writers also use this trick. Scammers spoof address lines to fool people into thinking an email has arrived from a legitimate source, such as an online bank. Similarly, virus writers have passed off viruses as security patches by spoofing their origin as being, for example, from Microsoft technical support.


A list of external email addresses, IP addresses and domains trusted by the entire organization or individual users. All mail from these addresses is delivered, bypassing the spam filters.


A malicious program that replicates itself and may cause damage to a computer system by attacking or attaching itself to boot information, another program or a document that uses macros.


A location to isolate files suspected spam emails that the files can't be opened, executed or delivered.