What is whitelist and blacklist data?

Question

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..

Answer 1

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.

Answer 2

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.

Answer 3

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.