In an explicitly enumerated category, blacklists and whitelists are logically equivalent and can be used interchangeably. In almost every other case blacklists are insufficient because new items can generally be created, either maliciously or just accidentally as the size of the category grows, which are not on the blacklist but which share whatever bad trait you were hoping to protect against.
I'm sure there are a few exceptions, but generally speaking any problem that can be solved with either a blacklist or a whitelist should use the whitelist, just to be safe. A problem that can't use a whitelist is probably not actually solvable by a blacklist either, and trying to use one is likely to fail in the long run.
Its indeed a very strange patch from Blizzard. As if they hastily assigned an intern to it and then called it a day.
^(?!facebook).*A blacklist won't allow items that match and a whitelist only allows items that match. Blacklists include by default and whitelists exclude by default.
Since the regex needs to match to be included - it is, by definition, a whitelist. It excludes by default anything that doesn't match. It just so happens the net being cast is so wide as to be "all except ____" where a whitelist is usually seen as "none except ____".
People would consider a blacklist that includes ` * .example.com` to be a list that contains all potential subdomains of `example.com`. With ` * ` being seen as shorthand.
E: Spaces around the asterisk added to avoid HN formatting.
[0] Technical limitations aside, especially in the context of URL matching since URLs have a maximum character length.
A list with one entry is also a list.
That regex will only positively "match" non-facebook items, and will only block facebook if implemented in a whitelist.
I'm just playing the straight man to your joke. Of course it's functionally a blacklist: That's what you asked for.
My comment is not a joke but a challenge to the parent ... that they are wrong
Yes whitelist are safer ... but whitelists can be cumbersome to generate/maintain and slow you down at runtime ...
On reddit let this slide , but here we have to correct the flawed thinking.
You cant run from engineering problems without consequece
So now we have graduated to course 202: how to make a blacklist safe?
Check context, and restrict access
I wrote a regex that would allow things that aren't facebook, and then you said "No, you're not allowing things that aren't facebook, you're not allowing things that don't match not being facebook".
If it's not a white-list, it's at least an opposite-of-black-list.
But then why do you need the blacklist?
I refer to this post by vec: https://news.ycombinator.com/item?id=16208419
If you think you need a blacklist you should probably be using a whitelist. If your problem can't be solved with a whitelist then it's probably better solved in a way that doesn't involve a blacklist or a whitelist.
ftfy