We present an approach for proactive malware detection by working on an abstract representation of a program behavior. Our technique consists in abstracting program traces, by rewriting given subtraces into abstract symbols representing their functionality. Traces are captured dynamically by code instrumentation in order to handle packed or self-modifying malware. Suspicious behaviors are detected by comparing trace abstractions to reference malicious behaviors. The expressive power of abstraction allows us to handle general suspicious behaviors rather than specific malware code and then, to detect malware mutations. We present and discuss an implementation validating our approach.