Be aware of scammers impersonating as IMDA officers and report any suspicious calls to the police. Please note that IMDA officers will never call you nor request for your personal information. For scam-related advice, please call the Anti-Scam helpline at 1800-722-6688 or go to

From defining key terms such as ""Spam Trap"" to outlining the rules governing unsolicited messages, this page serves as a valuable resource for individuals and organisations looking to comply with IMDA’s regulations on unsolicited communications.

Address Harvesting Software

This is a software that is designed or marketed for the purpose of trawling the Internet for e-mail address or mobile phone numbers, and then collecting and compiling these details into usable form for spamming.

Bayesian Filter

Bayesian analysis is a statistical procedure which attempts to estimate if an incoming e-mail is an unsolicited one based on the assessment results of the previous spam.


A list of e-mail addresses, domain names or organisations that are known sources of spam.

Dictionary Attack

A dictionary attack is a 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 "Johns" and "Marys" in various organisations, spammers are certain 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 address or other contact addresses.


E-mail (electronic mail) is the exchange of computer-stored messages by telecommunication. E-mail can be distributed to lists of people as well as to individuals.


In the context of spam, a filter is a program or section of code that is designed to examine the incoming email for specified criteria and then either allows or denies the email from reaching the end-users mailbox. See also blacklist and whitelist.

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.

Spam Trap

A spam trap refers to online forms that come with a pre-selected "option" to put that user on a mailing list. This pre-selection is often done with a view that it will go unnoticed by the user. So, when a user submits that form unwittingly, he would have appeared to have consented to being spammed by that organisation.

To avoid spam traps, users should make a habit of reading the entire form and be mindful of boxes that may need to be unchecked.

Trojan Horse

A Trojan Horse is a program which appears harmless, but contains malicious or harmful code. Once loaded into a 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.


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 a computer to help the spammers send out more of their material.


The opposite of a blacklist. That is, instead of being an explicit list of senders from whom e-mail will not be accepted or delivered, a whitelist lists out the "good" senders, so that all the e-mails from them will be accepted.