A first cavity-down ball grid array (BGA) package includes a substrate member and an array of bond balls. The array of bond balls includes a pair of parallel extending rows of outer mesh bond balls and a row of inner signal bond balls that is parallel to the pair of rows of outer mesh bond balls. A surface-mount blocking element is disposed between the row of inner signal bond balls and the pair of rows of outer mesh bond balls. The surface-mount blocking element is either a passive or an active component of the BGA package. In one example, the first cavity-down BGA package is surface-mounted to a second cavity-down BGA package to form a package-on-package (POP) security module. The surface-mount blocking element provides additional physical barrier against the probing of the inner signal bond balls. Sensitive data is therefore protected from unauthorized access.