There are more than 30 ways the PSNI can trace, identify or verify details about an individual in whom they have an 'interest'.
All these routes are covered by legal memorandums of understanding with the particular agencies which hold the details.
After its 1994 ceasefire, the IRA's intelligence-gathering arm - under the guidance of Belfast republican Bobby Storey - recruited and trained a six-strong team to specifically gather intelligence on senior law and police officers.
It exploited the more relaxed atmosphere of the time to trawl telecoms logs, BUPA records and installed a new recruit, law graduate John Tumelty, in a rented house at Strathearn Court in Holywood to carry out physical surveillance on the homes of judges and senior police officers in north Down.
In the event of the ceasefire breaking down, selected judges and police officers were to be assassinated in a 'night of the long knives'.
It's highly unlikely that any of the detail garnered by Tumelty and his fellow 'lilywhite' IRA recruits was used by dissident republicans to target the car of an Army major resting off-base in the Bangor area last week.
More likely he was followed from his Lisburn work location one day for a part of his journey to Bangor, then 'picked up' again en route to Bangor another day and followed again and again until his complete journey and destination was established.
Thereafter, attaching a small but powerful explosive device to his car was the simple part of the murder-plot.
It may be that another means of pinpointing the major and his nocturnal location was employed - a chance remark, or a specific reference to him, perhaps in an unguarded moment at a social gathering or during a formal meeting, could have betrayed his assignation.
There may, of course, be someone working in an official capacity with one of the 30 and more agencies with which the PSNI has legal memorandums of understanding who identified the major's whereabouts and betrayed his movements to the dissidents.
Such a means of betrayal is believed to have led to the IRA learning that Denis Donaldson was a British agent after 'Stormontgate' became public in 2002.
Shortly after papers referring to his intelligence role left the PSNI en route to the office of the Director of Public Prosecutions, Donaldson's secret spying role was divulged to the Provos, intelligence analysts reckon.
Evidently, today the dissidents - in particular the emerging Oglaigh na hEireann - has a volume of detail about the persons of interest to them for their terrorist purposes.
Whatever the means of eliciting information to establish the home addresses and vehicle registrations of persons of interest to them, the dissidents have obviously a reliable stream of information which they are carefully and sporadically utilising to target police and now senior military personnel.
A house in Grace Avenue in the Bloomfield area of east Belfast was used as a surveillance base by the IRA in 1994. A decade earlier, the home of civil servant Owen Connolly in the Belmont area was used to harbour gunmen who killed Maze Prison Governor William McConnell.
Leafy north Down is a fertile area for terrorists to survey given its attraction to members of the judiciary, senior civil servants and senior police officers as a safe residential environment.
The dissidents illustrated last week that those pleasant north Down avenues and the affluent suburbs around Bangor are now far from immune from their growing threat.