[PCI DSS 3.0] 6.2 Ensure that all system components and software are protected from known vulnerabilities by insta

6.2 Ensure that all system components and software are protected from known vulnerabilities by installing applicable vendor- supplied security patches. Install critical security patches within one month of release.

Note: Critical security patches should be identified according to the risk ranking process defined in Requirement 6.1.

6.2.a Examine policies and procedures related to security- patch installation to verify processes are defined for:
• Installation of applicable critical vendor-supplied security patches within one month of release.
• Installation of all applicable vendor-supplied security patches within an appropriate time frame (for example, within three months).

6.2.b For a sample of system components and related software, compare the list of security patches installed on each system to the most recent vendor security-patch list, to verify the following:
• That applicable critical vendor-supplied security patches are installed within one month of release.
• All applicable vendor-supplied security patches are installed within an appropriate time frame (for example, within three months).

There is a constant stream of attacks using widely published exploits, often called “zero day” (an attack that exploits a previously unknown vulnerability), against otherwise secured systems. If the most recent patches are not implemented on critical systems as soon as possible, a malicious individual can use these exploits to attack or disable a system, or gain access to sensitive data.
Prioritizing patches for critical infrastructure ensures that high-priority systems and devices are protected from vulnerabilities as soon as possible after a patch is released. Consider prioritizing patch installations such that security patches for critical or at-risk systems are installed within 30 days, and other
lower-risk patches are installed within 2-3 months.

This requirement applies to applicable patches for all installed software.