This question has originally been posted to Stackoverflow but then I found that this was the right place to ask. If you are a moderator, please delete this question at SO.
I am using Wappalyzer everyday as it provides me with some interesting data about the websites I visit.
Today I noticed that they actually sell full datasets/lists of sites using certain technology. You can see an example here:
The full list of 825,070 websites using WordPress costs US $1,575
Now, I know that most of those toolbar additions to your browsers actually collect information on the sites you visit and use them later on for statistics and other purposes (Alexa, visit count websites etc.). But the fact that these guys were actually selling it openly on their site, sounded almost as if someone would sell your email address publicly.
What am I aiming at?
Well, for $1,575 someone could get a really good base for doing some nasty things. They could hit all those websites and check the core versions and let's say plugins they use. After that they could filter the older ones and perform a series of attacks to infect visitors and spread out whatever they want.
The fact that an attacker would be able to get such huge already filtered list of websites, without any effort is what makes me question if this should be allowed to be done.
My questions are:
Is this legal?
What do you think about it?
Is selling website data widely done on the net?
I am asking more because of curiosity than getting really concerned. Having read that on their site made me feel it was not something completely normal.
If I'm wrong in something - please explain.