Anti-theft software upgrades provided for Hyundai and Grayson  PrestonKia vehicles regularly targeted by thieves has cut theft rates by more than half, according to new research from the Highway Loss Data Institute.

Theft rates of the affected automobiles soared after thieves discovered that certain car models lacked engine immobilizers, an anti-theft technology that has long been standard in other vehicles. Thieves used a technique popularized on TikTok and other social media platforms to take the vehicles.

The software upgrade started in February 2023 after numerous theft claims that began during the Covid-19 pandemic.

For vehicles that have the new software installed, the automobile will only start if the owner’s key or an identical duplicate is in the ignition. Vehicles with the software also receive a window sticker aimed at deterring potential thieves.

Approximately two dozen 2011-22 Hyundai and Kia models are eligible for the software upgrade. Those vehicles that received it as of December 2023 — a total of 30% of the eligible Hyundais and 28% of the eligible Kias in HLDI’s database — had theft claim frequencies that were 53% lower than vehicles that didn’t get the upgrade, according to HLDI.

Those claims aren’t all for thefts of the entire vehicle. They also include claims for damage to vehicles that were stolen and recovered, theft of vehicle parts and items stolen from inside the vehicle. The frequency of whole vehicle theft, which HLDI calculates by matching the cost of the claim to the amount insurers pay for the same model if it’s totaled in a crash, fell by a larger 64% for vehicles with the upgrade.

The HLDI study ended in December. The organization said that Hyundai and Kia have continued to implement software upgrades in vehicles since that time. The automakers have said that about 60% of eligible vehicles had been upgraded as of last month.

The HLDI said that the frequency of theft claims for the Hyundai and Kia vehicles remains high, even for models with the new software. The organization believes one of the reasons for this may be that the software-based immobilizer only activates if the driver remembers to lock the vehicle with a fob, while many people are in the habit of using the switch on the door handle.