The Windows XP activation algorithm has been cracked offline using Linux, The Register reports.

According to a blog post on Tinyapps, a site which catalogs tiny software made for Windows, the crack means that it’s possible to activate new Windows XP installations safely and securely offline. It’s worth noting that Windows XP has been cracked with tweaks and unofficial patches since its launch in 2001, but this crack allows people to activate XP offline without altering the OS whatsoever.

According to a subreddit discussing the crack, the software that allowed for it to happen has been around on the internet for months, and it’s not known who made and shared it or, as The Verge notes, where they got the program from.

The Register further reported that the product activation algorithm was cracked “some time ago”, and that in 2019 an open-source key generator was released which allowed for the printing of “endless Windows XP keys.” Last year someone shared a Windows executable that was capable of generating the confirmation ID codes necessary to complete the Windows XP activation process entirely offline, which is where the current activation algorithm defeating program derived from.

The program could be made freely available, as according to a Github discussion, a user called Neo-Desktop said they are reverse-engineering the software to create an open source version.

Despite being over 21 years old, Windows XP, once the world’s most popular OS, is evidently still not going anywhere. In September 2022, over eight years since Windows stopped supporting the operating system, it still managed to retain its popularity in some corners of the world, such as Armenia where it was the most used OS. And in September 2021 it was found that XP had a greater global share (0.59%) than Vista, its successor (0.26%).

Meanwhile, a 2019 study by SpiceWorks found that a staggering one in three US businesses still had at least one XP machine on their networks.