The number of jihadi sympathisers being closely monitored by garda and military intelligence in Ireland has swelled to more than 70.
The numbers were previously estimated at 30 or 40, but the network of suspects has grown, as surveillance is stepped up on those believed to be providing logistical support for Islamist activists based in Europe.
The 'top tier' here involves between 20 and 30 sympathisers, all known to have contact with suspected terror activists in Europe. It is believed they are providing logistical support like false documentation and identity papers as well as fundraising.
The second tier has more than 50 persons of interest, who are said to be involved in supplying similar back-up, but are not directly in contact with potential attackers.
Some of the sympathisers based here are also believed to have helped in the travel arrangements, such as supplying forged passports and other false documents for potential fighters heading out to what Isil describes as the 'Caliphate' (Syria and Iraq).
Foreign fighters have their documentation taken from them when they arrive in Turkey before they move on to Syria or Iraq - and are then in need of new identity papers if they are on their way back.
This makes the role of the logistics back-up cells so important, gardaí say.
The biggest fear now for police forces across Europe is those coming back from the Caliphate.
As a result of the defeats they have suffered in the region in the past year, Isil is now advising its potential recruits to stay where they are and carry out attacks in the countries where they live.
At least 30 people are known to have flown out to Syria and Iraq from here over the past few years, not all of them to join Isil with some joining the Kurds. They all have Irish passports.
Four are reported to have died there, including homegrown terrorist Khalid Kelly.
The sympathisers in Ireland are from several countries and are either living legally or are asylum seekers, hoping to secure status to remain here.
The 70-plus strong group includes many from North African countries, such as Algeria and Morocco, some from the Middle East, while others are from Pakistan and Egypt.
The threat level in this country from international terrorists remains at moderate, which means that an attack is possible but not likely. The level was raised after the 'Charlie Hebdo' attack in Paris in January 2015.
Garda and military chiefs have advised the Government that, even though an attack is unlikely in this country, they must be prepared on how to cope with the threat, apart from monitoring suspects and gathering and sharing intelligence with the UK and other European forces on a regular basis.
If there is a threatened attack, it is likely to come from what is termed a "lone wolf" imitating the actions of jihadis elsewhere by renting or stealing a vehicle and driving into a crowded area.
Similar vehicle attacks took place in Spain on Thursday and early yesterday as well as Westminster Bridge in central London in March and Stockholm in April.
Potential attackers could be radicalised either through online or social interactions, and selecting random targets.
A security exercise by the gardaí in June after a terrorist atrocity in London showed that heavily armed units could have responded to a terrorist incident in O'Connell Street, Dublin, within three minutes.
This is the result of saturation armed policing in the capital in response to the Kinahan-Hutch gangland feud.
There are nine armed support units deployed there along with two further patrols from the emergency response unit. Gardaí used GPS to verify the positions of those units at 10.06pm, the same time as the atrocity in London the previous Saturday night.
However, an attacker is equally likely to select crowds pouring out of a sports stadium or entertainment venue in Dublin or provincial cities. Since the start of the year, gardaí have been drawing up plans for temporary barriers to be erected around crowded areas to prevent attacks using trucks or other vehicles.
Those measures have been trialled for St Patrick's Day and Easter celebrations in Dublin as well as the Pride rally in June.
The use of barriers and bollards, capable of withstanding direct impact and preventing a vehicle from hitting its intended target, as well as a series of complex chicanes to slow down a driver, is planned to be extended in the coming months.
Officers have also been consulting colleagues in other countries on the tactics they have adopted for political summits and party conferences.