Note: This Glossary is for reference only. Readers are advised to refer to the UEM Ordinance for the statutory definitions of the relevant terms.

Address Harvesting Software Software that is specifically designed or marketed for use for searching the Internet or a public telecommunications network, and collecting electronic addresses such as telephone numbers or email addresses.
Brute Force Attack A brute force attack/search is a method to systematically enumerating all possible choices (e.g. email addresses or telephone numbers) and checking whether each choice exists (e.g. by dialling to each of the possible telephone numbers).
Dictionary Attack A dictionary attack is an automated means of generating e-mail addresses or other contact addresses by combining names, letters, numbers or symbols into numerous permutations. Since there are many "John" and "Mary" in various organisations, spammers are certain that they can reach at least one of them once they spam them all. This can happen even if the recipients have never published their e-mail addresses or other contact addresses.
Do-not-call Registers

Do-not-call Registers are registers of electronic addresses (such as phone, fax and SMS/MMS numbers) established by CA under section 31 of the Ordinance. Their purposes are to provide:

  1. registered users of electronic addresses with a convenient means by which they may notify senders of commercial electronic messages that they do not wish to receive such messages; and
  2. senders of commercial electronic messages with a convenient means by which they may ascertain whether a registered user of an electronic address does not wish to receive commercial electronic messages at that electronic address.
Header Header is machine-generated information about the source or routing of the electronic message such as calling line identifications or IP addresses.   It does not include the 'from' field in email message which can easily be altered by senders.
Message Transfer Agent (MTA) An MTA is a program responsible for receiving, routing, and delivering e-mail messages. MTAs receive e-mail messages and recipient addresses from local users and remote hosts, perform alias creation and forwarding functions, and deliver the messages to their destinations. An MTA is sometimes called a mail transport agent, a mail router, an Internet mailer, or a mail server program.
Open Relay An Open Relay is an e-mail Message Transfer Agent that will deliver any e-mail for any sender. Spammers seek out these servers as a free ride for their messages.
Trojan / Trojan Horse A Trojan Horse is a program which appears harmless, but contains malicious or harmful code. Once loaded into your computer system, it can wreak damages on the sly, such as ruining the file allocation table or hard disk. A Trojan horse may be widely redistributed as part of a computer virus.
Virus A virus is a programming code often disguised as something else that causes some unexpected and usually undesirable event. A virus is often designed so that it is automatically spread to other computer users. Many of the e-mail spam contain virus attachments that can infect your computer to help the spammers send out more of their material.
Zombie Computer A computer attached to the Internet that has been compromised by a hacker, a computer virus, or a Trojan program.  Such computers are usually used to perform malicious tasks such as spamming under remote direction, with the owner normally unaware of such tasks.