Passwords must not contain the user's entire samAccountName (Account Name)
value or entire displayName (Full Name) value. Both checks are not case
sensitive:
The samAccountName is checked in its entirety only to determine whether it
is part of the password. If the samAccountName is less than three characters
long, this check is skipped.
The displayName is parsed for delimiters: commas, periods, dashes or
hyphens, underscores, spaces, pound signs, and tabs. If any of these delimiters
are found, the displayName is split and all parsed sections (tokens) are
confirmed not to be included in the password. Tokens that are less than three
characters in length are ignored, and substrings of the tokens are not checked.
For example, the name "Erin M. Hagens" is split into three tokens: "Erin," "M,"
and "Hagens." Because the second token is only one character long, it is
ignored. Therefore, this user could not have a password that included either
"erin" or "hagens" as a substring anywhere in the password.
( src )
There is a very easy method to detect such 'weak' passwords -- compute Levenshtein distance between password entered and account name, full name, other user's data (if known: D.O.B., address, maiden name, etc).
More about Levenshtein distance.
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