There is no silver bullet for security. The threats are as dynamic as the technologies upon which they prey. A systemic approach to security should always be considered.
I suggest regular security audits and the enforcement of their recommendations as the most important security tool. Software always needs to be patched; passwords need to be rotated; only pre-defined servers should be allowed to communicate with each another using specific protocols. Unauthorized wireless access points need to be detected; user access rights and controls need to be periodically reassessed. E-mail needs to be consistently scanned and intrusion detection and prevention systems need to be monitored.
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