Trend Micro has made the free anti-spyware tool Hijack This an open source application.
Trend Micro bought the freeware tool from its Netherlands-based creator Merijn Bellekom in 2007.
It can be used to scan a computer to find settings changed by spyware and malware and to generate log files that can be used to identify infections.
Trend Micro initially bought the tool to get a better sense of spyware in the wild.
The company modified the tool slightly to allow users to submit files to the vendor for analysis, according to a report by NetworkWorld at the time.
However, prior to the buyout, the log files were generally uploaded to internet discussion forums by users seeking a diagnosis of computing problems.
Open-sourcing the tool meant it would continue serving these online communities, the company said.