An IT security expert says it is very difficult to "secure every little corner" of the police national computer.
Yesterday fears were raised that the network was compromised during an alleged Israeli spy incident in Christchurch.
Police are confident their systems are secure, but Daniel Ayers told TV ONE's Breakfast it is impossible to be certain.
Ayers said police use the national intelligence application (NIA) to access information about criminal histories and general intelligence and anyone who holds a driver's licence would be in the system.
The case has highlighted growing concern about identity fraud, and that Israelis have stolen NZ passports before.
Ayers told Breakfast this morning that the police computer network is extensive and "it's very difficult to secure every little corner of it".
He said these types of organisations don't volunteer a lot of detail as to how they work but it still should be relatively difficult for people to get into the system and they would need to get physical access to a police computer.
Commenting on reports yesterday that someone could just walk up to a police computer and plug in a USB to get access, Ayers said it is best practice in the industry to lock things down and that should not be possible.
"But ultimately, given enough time, if someone does have physical access then there's risks."
Police take computer security seriously and are well aware of all the risks, Ayers said.
However, he said with the large number of police across the country "there's always the possibility that one or two may not be as trustworthy as you would like".
Ayers said while it is all theoretical and we don't know what, if anything, has happened there are thousands of legitimate queries every day and it would be very difficult to be absolutely certain that there hasn't been unauthorised access.
However, Ayers said if it was simply a question of people wanting to steal relatively low volumes of identities "there are probably easier ways of doing it".
And he said given the suspicion raised police would have thoroughly checked their systems.
"If there was latent security problems in there I think they would have found them."
Acting Chief Information Officer Murray Mitchell said yesterday police systems were subject to regular security audits and intrusion checks.