Malware-Testing Service Scan4You Convicted on Three Federal Charges

What I really don't understand is that the same services exist, but inverted, for not only acceptable but _recommended_ use cases. (e.g. it's common in some of the P2P communities I participate in to treat some of these virus scanning sites as a "broad filter" initial vetting for questionable items) Without these services, I would have, on multiple occasions in the past, installed rootkits.

What differentiates from a site saying "your executable is safe" from saying "your malware wasn't detected"? Is it really an aspect of Intent in the law? I find this highly worrying absent comforting words from someone actually versed in the legal framework.