Has your computer been infected with a suspected NSA spying implant? A security researcher has come up with a free tool that can tell.

Luke Jennings of security firm Countercept wrote a script in response to last week’s high-profile leak of cyberweapons that some researchers believe are from the National Security Agency. It's designed to detect an implant called Doublepulsar, which is delivered by many of the Windows-based exploits found in the leak and can be used to load other malware.

The script, which requires some programming skill to use, is available for download on GitHub.

Some security researchers have used Jennings's script to scan the internet for machines infected with the implant. Their results have varied widely, showing between 30,000 and 100,000 computers with the code on them.

Below0Day, a penetration testing company, has tweeted graphs showing which countries are most affected. The U.S. sits at the top, with 11,000 machines.

Several other countries, including U.K., Taiwan and Germany, have more than 1,500 machines infected.

It’s not clear when these machines were infected with the implant, Jennings said. However, the suspected NSA exploits that deliver Doublepulsar were leaked a week ago, at which point anyone with some hacking skills could start using them.

Security experts are worried that cybercriminals or foreign governments might take the leaked exploits and attack vulnerable machines over the internet. They say computers with older or unpatched Windows systems are particularly at risk. Rebooting a system will remove the implant, but not necessarily any malware associated with it.

Jennings said he developed his script by analyzing how the Doublepulsar implant communicated over the internet to its control server. However, his original intention was to help businesses identify the implant over their networks, not to scan the entire internet for the implant.

“There’s been a lot of discussion on Twitter,” he said. “People are wondering if maybe the script is incorrect, because they are surprised by the number of systems infected.”

However, not one has presented evidence that his computer script is wrong, Jennings said.

"There’s probably a group out there, or many out there, using these exploits to compromise vulnerable machines,” he said.

Older Windows Server systems, especially those running without a firewall, are considered easy to hack with the exploits. Thousands of these machines around the internet appear to be exposed.

Dan Tentler, CEO of security provider Phobos Group, has been looking at the accuracy of the script. He’s already done manual checks on 50 machines that were flagged as infected, and all 50 of them were.

“Usually if you check that many, and the scripting is bad, you would expect to find a handful that were false positives,” he said. “But I’ve found zero false positives.”

It’ll take more time for security researchers to vet the accuracy of the Doublepulsar search results. But Tentler recommends system operators take steps to prevent infection from the recently leaked malware.

Users should install all available patches on their Windows system, he says. Past patches from Microsoft will address the danger, but older operating systems like Windows XP and Windows Server 2003 no longer receive support from the company.

Users can consider upgrading the system to a newer OS. They can also run antivirus products like Windows Defender to help them root out any malware.