Cisco Cisco Email Security Appliance X1070 Fehlerbehebungsanleitung
How Smart Identifiers Work
Document ID: 118543
Contributed by Cisco TAC Engineers.
Oct 10, 2014
Contents
Introduction
Credit Card Numbers
U.S. Social Security Numbers
CUSIP Numbers
ABA Routing Numbers
Credit Card Numbers
U.S. Social Security Numbers
CUSIP Numbers
ABA Routing Numbers
Introduction
This document describes smart identifiers, which are built−in content scanning patterns that detect certain
types of data. For this release, the system will implement smart identifiers for credit card numbers, U.S. Social
Security numbers, CUSIP numbers, and ABA routing numbers.
types of data. For this release, the system will implement smart identifiers for credit card numbers, U.S. Social
Security numbers, CUSIP numbers, and ABA routing numbers.
Internally, a smart identifier consists of a regular expression that matches candidate strings, along with a
validation function that checks the candidate match in some way. For example, the validation function for a
credit card number ensures that the check digit is correct.
validation function that checks the candidate match in some way. For example, the validation function for a
credit card number ensures that the check digit is correct.
The regular expressions for each smart identifier will include word boundary anchors ('b') at both ends. (This
prevents the system from matching a U.S. social security number, for example, in the middle of a longer string
of digits.) For simplicity, these are omitted from the descriptions below.
prevents the system from matching a U.S. social security number, for example, in the middle of a longer string
of digits.) For simplicity, these are omitted from the descriptions below.
The smart identifiers implementation must be careful about overlapping matches, because a substring found
by the regular expression may not validate. For example, a filter is scanning for credit card numbers against
the string 9999 4321 9999 9999 9995 1234 5678 9000 should find the valid credit card number 4321 9999
9999 9995, even though a simple regular expression scan for possible numbers would find 9999 4321 9999
9999 and 9995 1234 5678 9000.
by the regular expression may not validate. For example, a filter is scanning for credit card numbers against
the string 9999 4321 9999 9999 9995 1234 5678 9000 should find the valid credit card number 4321 9999
9999 9995, even though a simple regular expression scan for possible numbers would find 9999 4321 9999
9999 and 9995 1234 5678 9000.
Credit Card Numbers
A credit card number begins with a variable length card type, which indicates whether the number is a VISA,
MasterCard, AMEX, etc., and ends with a check digit. Different card types use different numbers of digits in
the entire number, but the check digit calculation is the same in each case.
MasterCard, AMEX, etc., and ends with a check digit. Different card types use different numbers of digits in
the entire number, but the check digit calculation is the same in each case.
Note that enRoute or JCB cards are not matched. Also, 13−digit VISA numbers do not exist, and won't be
matched in our implementation.
matched in our implementation.
16−digit credit card numbers will match one of the following regular expressions:
[0−9]{4}−[0−9]{4}−[0−9]{4}−[0−9]{4}
[0−9]{4}\.[0−9]{4}\.[0−9]{4}\.[0−9]{4}
[0−9]{4} [0−9]{4} [0−9]{4} [0−9]{4}
[0−9]{16}
[0−9]{4}\.[0−9]{4}\.[0−9]{4}\.[0−9]{4}
[0−9]{4} [0−9]{4} [0−9]{4} [0−9]{4}
[0−9]{16}