It is becoming increasingly difficult to tell whether one's PC has been broken into and turned into a zombie, according to an internet security company.

Comodo cited a recent article that appeared in ComputerWorld which said that " ... a virus takes over your PC [and] it receives instructions over the internet to mass mail spam".

Currently the company has said that it is focussing on methods to prevent PCs from being broken into in the first place and that it is to integrate these methods into its existing firewall product.

Melih Abdulhayoglu, chief executive and chief security architect of Comodo, said: "Our goal is to change the face of security.

"Instead of trying to determine whether a file is 'bad' once it is on your computer, it is far more logical to prevent the breach in the first place."

The company's new product that features this preventative methodology is dubbed Firewall Pro V3.0 and contains a list of more than 600,000 applications that the company has deemed to be safe.

To be available in a few weeks, Firewall Pro V3.0 will be free to download and has capabilties that are more often seen in security applications directed at businesses.

Comodo has over 200,000 business customers and its products are used by more than three million private users.