The past 3 years have seen many organizations adopt and deploy in-house dynamic sandboxing technologies tasked to detect and block specific classes of malware. Most advocates of the approach will point to malware samples that were detected via the sandbox, but missed by conventional antivirus signature systems, and seek to justify the investment through these simple metrics.
A well maintained sandbox system - capable of launching a dozen or more virtual systems running a vanilla Microsoft Windows installation - is sufficient enough to detect a high percentage of the mainstream malware in circulation, and is perfectly suited to detecting serial variants generated by popular malware construction kits (assuming that no anti-virtual machine evasion code has been included).
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Even if that was possible, malware sandboxing approaches will only capture the threats that come in through the front-door -- not threats that get transported between networks via roaming devices. So, as business operations embrace the cloud, BYOD, VPN dual tunneling, and expand their home-office workforce, centralized sandboxing approaches will rapidly diminish in efficacy -- and malware authors continue to have the upper-hand.