A system sending e-mail terror alerts to the public is being launched by security chiefs at MI5.
Dame Eliza Manningham-Buller has warned over the terror threat
People will be able to register on the MI5 website to receive updates when the threat level changes.
The initiative follows considerable interest in similar information for the public introduced in August on the MI5 and Home Office websites.
MI5 chief Dame Eliza Manningham-Buller recently warned that it was tracking at least 30 terror plots against the UK.
Whitehall says the move to introduce e-mail terror alerts has been in the pipeline for a while.
Members of the public can also register to be notified of any other new information posted on the MI5 website.
The Home Office says it is part of a long-planned programme of reaching out to the public and keeping it better informed about the terrorist threat.
Plans to extend the service to sending text messages to mobile phones are also being considered.
There will be two types of service on offer initially.
The BBC's security correspondent Gordon Correra explained people were "not actually getting anymore information than they can get at the moment" but "that information is being made more easily available".
"They [MI5] are kind of feeling their way into engaging with the public more and that's partly that what they used to do was so closed and so secret - the world of espionage and spies," he said.
"But in the world of terrorism there is a realisation they need to be more public."
But he added that one of the difficult questions was what people should do about the information when they receive it: "There's not necessarily that much information on the website about how you should act and how you should respond other than being vigilant and calling a hotline if you see anything suspicious."
Text messages will update the public on threat levels
The first, called Threat Level Only, will inform the recipient if the nationwide terror threat level changes. The condition is currently listed as severe.
The second more inclusive service is called What's New, and will be a digest of the latest information from MI5, including speeches made by the director general and links to relevant websites.
The level of the terror threat to the UK is assessed by the government's Joint Terrorism Analysis Centre.
The current threat is set at the second highest level, "severe", which means an attack is considered "highly likely".
In November, Dame Eliza, MI5's director general, warned the terror threat was "serious" and "growing", and that 1,600 individuals were being kept under surveillance.
Steve Aukstakalnis works for a company in the United States, Alerts USA, which provides a similar service.
He told BBC Five Live: "We'll send an initial 'heads-up' message via the text, but you're limited to about 130 characters in that message.
"We follow this up with streaming audio - both live and on demand - which gives additional details, event analysis, further response guidance where necessary and so on, to provide a little bit more of a robust service."