Kiwis with a home detention bracelet have taken to social media exposing a flaw that allegedly prevents Corrections knowing where they are, although Corrections are adamant that their systems can detect when a person tries to interfere with their tracker.
A man said wrapping the bracelet in tin foil could prevent it from reporting its location.
Others suggested using a foiled supermarket chicken bag.
"I did it with my best friend so he could come clubbing," one person claimed.
Another wrote: "If the signal is GPS, it should block with enough tin foil. I put some on my phone to block my GPS signal and it seemed to work."
However, Corrections deputy national commissioner Andy Milne says "our systems can detect when a person is attempting to interfere with their tracker, which enables us to take action".
Milne said any time that a person's electronic monitoring equipment wasn't functioning as expected, Corrections responded as a priority, and notified police.
"This has led to 18 arrests by police over the past 12 months.
"Anyone found in breach of the conditions of their electronic monitoring can be prosecuted, which can lead to imprisonment. Corrections can also apply to the Court to have an offender's sentence cancelled and replaced with imprisonment. They may also jeopardise their ability to be granted bail or sentenced to a community based sentence in future.
"Electronic monitoring is widely used by law enforcement and corrections jurisdictions internationally, and other countries face similar issues with offenders attempting to manipulate the monitoring system.
"We continue to upgrade our systems to detect and respond to any attempts made by offenders to subvert their monitoring. Ongoing advances in technology and regular software upgrades means that our electronic monitoring provider is able to provide us with more sophisticated data and information than ever before."
Milne, who said that Corrections are currently electronically monitoring 4,688 offenders in the community and defendants on bail, also rejected claims trackers could be temporarily disabled through being submerged in water.
"All trackers are designed to be water resistant to allow offenders to undertake normal daily activities. Submerging a tracker does not prevent ongoing monitoring.
"Electronic monitoring can provide an offender or defendant the opportunity to remain residing in the community, rather than going to prison. The majority of offenders go on to comply with their conditions in the community."
Milne also said that the tracker that was "spoofed" at the 2014 Kiwicon event was a GWG tracker from Taiwan.
"The Department has never used this company for electronic monitoring."
A top hacker had claimed to demonstrate in 2014 how home detention bracelets could be fooled into letting criminals roam free.
William Turner claimed to show he could defeat electronic monitoring bracelets that relied on the cellular phone network through a practice known as "spoofing".
Turner, known in the industry as Ammon Ra, had showed Wellington's Kiwicon conference how a bracelet could be wrapped in foil, preventing it from reporting its location, then the signal mimicked by a laptop using a $500 transmitter and custom software.
Turner then instructed the "spoof" transmitter to report movements, despite the hacker and his bracelet remaining on stage.
"And here it is now, it shows tracking down the road," he said, to applause from the audience, as the signal showed him apparently moving down Courtenay Place.
Turner used a bracelet made by Taiwanese firm GWG International.
Corrections said their bracelets in 2014 were made by British firm Buddi, but from 2015 were made by United States company 3M.
In 2014 Corrections confirmed its systems relied on the cellular network, but believed they were resistant to problems identified by Turner.
At the time Turner told the Herald the electronic bracelet problems should "probably" be fixed, as criminals could exploit the flaws.
"But I don't really care, I'm doing it for fun, not social justice. I don't think there's a non-criminal application for it."
At the time, the Rethinking Crime and Punishment director said there was a danger in Corrections relying on electronic monitoring when in-person checks would provide greater surety.
"There is a temptation towards a simplistic mechanism. Ultimately not just victims, but people out there in the community, will benefit if we are doing everything we can to reduce the chance of reoffending," he said.
However, at the time Corrections disagreed that Turner's foil hack would work, and highlighted that anyone trying to tamper with the home detention trackers could face criminal charges.
"To date our electronic monitoring system has proved reliable and accurate," Corrections Services national commissioner Jeremy Lightfoot said.
But one person on social media claimed he'd been on old and new trackers, and the foil hack worked on both devices.
He also highlighted a submerging technique that he said allowed him to leave his home undetected for 15 minutes at a time.
"They tried to say I couldn't submerge the latest type because the water would block signal. I tested the s*** out of it. I started by submerging it for 15 minutes then I'd wait a day and no one came," an offender wrote on Facebook.
"Finally I stretched it out for 60 minutes submerged. No one came. Not once. The bracelet sends a repeating signal to a receiver every two or so minutes but the GPS only pings your bracelet every 15 minutes."
In 2014 more than 1700 people were on home detention and wearing ankle bracelets.