The new specialised National Gang Unit is being described as the same policing with a different name.

The latest gang-fighting tools to be introduced by police are part of a long line in a combat that's constantly evolving.

With international organised crime groups reaching into New Zealand police and customs and law enforcement have had to lift their game with cops going back to their old methods of catching criminals.

Police are returning to crime-fighting ways of old in their fight against gangs, as technology becomes harder to hack, experts in New Zealand's criminal underworld say.

In light of the recent police announcement on national and local gang units, today's episode of The Detail looks at how police and governments have fought back against gangs over the decades.

New Zealand Herald investigative reporter Jared Savage has been focusing mostly on gang-related crime and justice stories for the last half-decade. He's also written a couple of books - Gangland and Gangster's Paradise.

He says the introduction of methamphetamine in the late 1990s and early 2000s "supercharged the criminal underworld in which gangs belonged to".

"Then around 2015 we started seeing a bit of a sea change. It wasn't just local gang members and local organised crime figures working together locally to import drugs into the country, we actually started seeing organised crime groups reaching into New Zealand.

"The police and customs and law enforcement have had to lift their game."

Savage says this means cops have had to go back to their old methods of catching criminals - before cellphones were even a thing.

"Fifteen-twenty years ago, everyone was carrying Nokia handheld cellphones around and criminals were too. They were communicating via text messaging and phone calls. The police were able to intercept these text messages and phone calls...and present that in evidence.

"The introduction of smart phone technology and apps on people's phones - different ways of communicating - mean most people don't send text messages anymore, they use Facebook Messenger or WhatsApp and many other apps that are out there - which are encrypted end-to-end, so the police can't intercept those like they used to.

"That's made it a lot harder to investigate these different groups.... so the police sort of changed their methods and it becomes a game of cat-and-mouse between the criminal world and the covert investigation world."

Police have upped their physical surveillance and put listening devices in homes and cars, Savage says.

Beyond that, public policing operations have helped police get some "good results"…

Go to this episode on rnz.co.nz for more details