Security researchers are warning that Internet users who install pirated versions of Microsoft’s latest Windows 7 operating system may also be installing malicious software, too. Experts at Atlanta-based security firm Damballa say they first noticed hacked versions of the Windows 7 release candidate available on peer-to-peer file-sharing networks and newsgroups last week, shortly after the OS was released to developers. Damballa found that computers with the tainted versions of Windows 7 were programmed to silently reach out to an Internet server to check for further updates, which in this case is a piece of malware that Kaspersky Antivirus calls Win32.Banload.cdk. “The first thing this does is phone home and get a list of additional malware to install,” said Tripp Cox, vice president of engineering at Damballa. Damballa managed to grab control over the server that’s contacted by the pirated Windows 7 versions — codecs.systes.net — which is how it knows