(n.) (1) A method used to break security systems, specifically password-based security systems, in which the attacker systematically tests all possible passwords beginning with words that have a higher possibility of being used, such as names and places. The word "dictionary" refers to the attacker exhausting all of the words in a dictionary in an attempt to discover the password. Dictionary attacks are typically done with software instead of an individual manually trying each password.
(2) An e-mail spamming technique in which the spammer sends out thousands or millions of e-mails with randomly generated addresses using combinations of letters added to known domain names in the hopes of reaching a percentage of actual e-mail addresses. For example, a dictionary attack list might begin with firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, and so on until all possible combinations of letters and numbers has been exhausted.