Cnet has come under fire for wrapping downloads of the popular Nmap network analysis tool and other open-source software packages with a toolbar of dubious utility.

Nmap is a popular open-source network auditing and penetration-testing tool that allows sysadmins to run network troubleshooting and penetration tests. Over the last few days, users who have downloaded the tool from Cnet popular download.com site have been, by default, offered it in conjunction with the Babylon Toolbar.

Sysadmins can opt out of receiving the toolbar, which changes their browsing experience, home page and default search engines, but they are clearly directed towards accepting the software, as a blog post by Sophos illustrates.

Gordon Lyon (Fyodor), the developer of Nmap, has cried foul over the way the toolbar has been pushed, objecting in a post to the North American Network Operators' Group (Nanog) mailing list (extract below).

The problem is that users often just click through installer screens, trusting that download.com gave them the real installer and knowing that the Nmap project wouldn't put malicious code in our installer. Then the next time the user opens their browser, they find that their computer is hosed with crappy toolbars, Bing searches, Microsoft as their home page, and whatever other shenanigans the software performs! The worst thing is that users will think we (Nmap Project) did this to them!

Lyon added that consumers downloading VLC, the popular open-source media player software, are also being offered the Babylon toolbar, via what he described as a a "Trojan installer".

Several anti-virus firms apparently agree with this assessment because Cnet's Nmap installer is already detected as a Trojan by BitDefender and F-Sc and as a potentially unwanted program by Panda, McAfee and others, according to VirusTotal (here).

Our own incomplete checks suggest that only Windows users are offered the Babylon Toolbar when they download VLC.

Paul Ducklin, Sophos's head of technology, Asia Pacific, shares Fyodor's concerns, arguing that download.com should be offering the toolbar only to those make an informed choice to use it, via an opt-in process.

"A software installation for product X which attempts to foist an unrelated product Y onto your computer by default is poor security practice," Ducklin writes. "Anything outside the obvious remit of the installer should be clearly and unequivocally opt-in, not opt-out."

We asked Cnet to respond to these criticisms and will update this story as and when we hear back with an explanation about its business practices in this area. ®