Attacks on industrial control systems and critical infrastructure assets are on the rise. These systems are at risk due to outdated technology and ad hoc security measures. As a result, honeypots are often deployed to collect information about malicious intrusions and exploitation techniques. While virtual honeypots mitigate the excessive cost of hardware-replicated honeypots, they often suffer from a lack of authenticity. In addition, honeypots utilizing a proxy to a live programmable logic controller suffer from performance bottlenecks and limited scalability. This chapter describes an enhanced, application layer emulator that addresses both limitations. The emulator combines protocol-agnostic replay with dynamic updating via a proxy to produce a device that is easily integrated into existing honeypot frameworks.