In this paper, we overview cluster security research underway at Mississippi State University (MSU) and focus on one particular effort involving a process to model system vulnerabilities and possible exploitations in specific cluster environments using exploitation graphs (e-graphs). Cluster security research at MSU has included attacks against clusters, anomaly detection, sensor fusion, VGLI security functionality in clusters, and the use of known system vulnerability data, system configuration data, and vulnerability scanner results to create e-graphs to model possible attack scenarios. The use of e-graphs is helpful in determining attacker work factor analysis, cost/benefit analysis of security, detection of attacks, and identification of critical vulnerabilities.