They fight off viruses, malware, exploits, etc so I think mostly we should consider this a classification problem only from where we sit. Most of the net works

They fight off viruses, malware, exploits, etc so I think mostly we should consider this a classification problem only from where we sit. Most of the net works too - AdBlock, NoScript and Ghostery wouldn't be amongst the most popular extensions on multiple browsers if they had many negative consequences.