PCI DSS specifies 12 different requirements to secure cardholder data and requires a qualified assessor to examine a merchant's environment to ensure compliance. Penalties for non-compliance range from small fines to the inability to use a specific type of credit or debit card.
Specific to risk assessment, the PCI DSS standard requires that "security controls, limitations, network connections and restrictions" are tested at least annually. It also mandates quarterly use of a wireless analyzer to see if your Wi-Fi networks are vulnerable. Additionally, the regulation requires quarterly vulnerability scans to ensure that no known vulnerabilities put cardholder data at risk.
I strongly recommend that organizations also conduct a more formal penetration test, ideally performed by outside resources, at least once a year, and also use automated pen testing tools internally more often. Why? Because the bad guys are testing your network and applications every day. They are performing risk assessments all the time, trying to figure out how to compromise your systems, so you should use their same tools and techniques to find and remediate problems.
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This was first published in October 2007