I was reading about development of XPCOM component. I came across these terms called whitelist data and blacklist data, I tried to find out on google but couldn't .. I do not know how its related to programming so forgive me if I placed the question at wrong place..
White lists and black lists are two ways of filtering data. If you have a white list then you will filter in only data on the white list; if you have a black list you will filter out only data on that list.
For example, consider automatically rejecting incoming phone calls. You could have a black list of marketing companies, so everyone but them would be able to call you. Or you could have white list containing your friends' numbers, so only they would be able to call you.
TL;DR:
- Whitelist - only these things.
- Blacklist - everything but these things.
I don't know how it pertains to your XPCOM component, but in general terms:
- A whitelist is a list of things that you know are good
- A blacklist is a list of things you know are bad.
A spam filter would be a good example - you have a whitelist of people you're willing to receive email from without checking for spam, and a blacklist of known spammers whose emails get automatically deleted. Emails from anyone not on either list might be examined using a Bayesian filter (or similar) to determine whether they look like spam or not.
From Wikipedia:
Blacklist: In computing, a blacklist is a basic access control mechanism that allows everyone access, except for the members of the black list (i.e. list of denied accesses). The opposite is a whitelist, which means allow nobody, except members of the white list. As a sort of middle ground, a greylist, contains entries that are temporarily blocked or temporarily allowed. Greylist items may be reviewed or further tested for inclusion in a blacklist or whitelist.
Whitelist: A whitelist (or white list) is a list or register of entities that, for one reason or another, are being provided a particular privilege, service, mobility, access or recognition. As a verb, to whitelist can mean to authorize access or grant membership. Conversely, a blacklist is a list or compilation that identifies entities that are denied, unrecognized, or ostracized.
Bruce Schneier has an excellent explanation of black-list vs. white-list in context of computer security: https://www.schneier.com/blog/archives/2011/01/whitelisting_vs.html.
Physical security works generally on a whitelist model: if you have a key, you can open the door; if you know the combination, you can open the lock. We do it this way not because it's easier -- although it is generally much easier to make a list of people who should be allowed through your office door than a list of people who shouldn't--but because it's a security system that can be implemented automatically, without people.
To find blacklists in the real world, you have to start looking at environments where almost everyone is allowed. Casinos are a good example: everyone can come in and gamble except those few specifically listed in the casino's black book or the more general Griffin book. Some retail stores have the same model -- a Google search on "banned from Wal-Mart" results in 1.5 million hits, including Megan Fox -- although you have to wonder about enforcement. Does Wal-Mart have the same sort of security manpower as casinos?
white list is a list where you can use it for further need in your application as the functionality proceeds and black list is one which you are not interested in entertaining as you further proceed forward in your application.
来源：https://stackoverflow.com/questions/1453285/what-is-whitelist-and-blacklist-data