Trend Micro has made the free anti-spyware tool Hijack This an open source application.
The company said it would "maintain the original source code and ... update the base code on SourceForge as developers make modifications".
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.
