Those tempted to download software cracks to unlawfully activate software from a trial mode into a paid mode have been warned that they may be unknowingly installing hacking tools onto their system.

TrendLabs, the research arm of PC security firm Trend Micro, said two out of the five most prevalent hacking tools in circulation have been actively downloaded by users seeking to extend the trial period of commercial software.

The company said such tools are often downloaded via P2P (peer-to-peer) networks or websites hosting illegal software, but users are unaware that the downloads surreptitiously install malicious software on PCs. The software can then be used by hackers to steal personal information including financial data, TrendLabs said.

"We estimate that approximately 16 percent of PCs worldwide are infected with hacking tools. In many cases, computers are being infected by users downloading software cracks and visiting illegal software download sites," said David Sancho, Senior AV Researcher at Trend Micro.

"The objective is often to avoid paying thirty pounds for a piece of software, however, consumers should in fact realise that it could cost them hundreds of pounds in the long-term."