October 21, 2013
Is Knowledge-Based Authentication Still Effective?
"What is your mother's maiden name? Your oldest daughter's middle name?" Online help sessions or call centers often ask the user to provide answers to a "secret" question or set of questions most often when the user has forgotten an account password and needs to retrieve it or select a new one. This authentication process is called knowledge-based authentication (KBA). The assumption is that if the person knows the correct answers, then that person is the authentic accountholder.
I recently attended a security conference where a panel of security authentication experts all stated that any extra protection KBAs provide is minimal. The high-profile data breaches that we've read about, along with the over-disclosure of personal information on social media sites, often make the answers to these questions easily available. These experts called for the abandonment of KBAs. In further support of this position was a recent article by Brian Krebs (Krebs on Security) that detailed how an identity theft service had hacked into some of the country's largest aggregators of consumer and business information. This service then tried to sell the data over the Internet, compromising the effectiveness of KBAs.
KBA questions can be either static or dynamic. Those that are static instruct the user to select from a list of preformulated questions—such as "What is your mother's maiden name?" Some sites allow users to create their own questions. In either case, the Q&A process is normally done when the user creates the account and selects the password. Dynamic KBAs are created by the website entity and generally request a response to a series of multiple-choice questions created from data not readily available in the public domain—for example, "Select a previous address from the list."
The formulation of KBA questions requires a careful balancing act between making answers easy enough for the authentic user to retain and making them difficult for an outsider to find the answer by looking through public databases and social media sources.
The June 2011 Federal Financial Institutions Examination (FFIEC) supplemental guidance on authentication for Internet banking states about KBAs that "institutions should no longer consider such basic challenge questions, as a primary control, to be an effective risk mitigation technique." The guidelines support the more sophisticated dynamic KBAs, adding this caution: "Although no challenge question method can mitigate all threats, the Agencies believe the use of sophisticated questions as described above can be an effective component of a layered security program." But we have to ask, have the breaches of the data sources often used to create the dynamic KBAs that have taken place since the issuance of this guidance so weakened them as to negate their value?
To enhance dynamic KBA programs, institutions can time the answer input intervals, tally missed questions, and employ other factors to essentially score the KBA session, which could signal that a criminal is posing as the legitimate customer.
No matter how many questions there are, KBAs are just one identification form factor—the "something you know" part of three-factor authentication. The FFIEC recommends that multiple form factors—including the "something you have" and "something you are" components—be used with higher-risk transactions. These should be used to support a stronger security process under a layered security approach.
Portals and Rails is interested in knowing how your institution currently uses KBAs, and if recent events will change their use.
By David Lott, a retail payments risk expert in the Retail Payments Risk Forum at the Atlanta Fed
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