Network intrusion detection is a crucial task in ensuring the security and reliability of computer networks. In recent years, machine learning algorithms have shown promising results in identifying anomalous activities indicative of network intrusions. In the context of intrusion detection systems, novelty detection often receives limited attention within machine learning communities. This oversight can be attributed to the historical emphasis on optimizing performance metrics using established datasets, which may not adequately represent the evolving landscape of cyber threats. This research aims to compare four widely used novelty detection algorithms for network intrusion detection, namely SGDOneClassSVM, LocalOutlierDetection, EllipticalEnvelope Covariance, and Isolation Forest. Our experiments with the UNSW-NB15 dataset show that Isolation Forest was the best-performing algorithm with an F1-score of 0.723. The result shows that network-based intrusion detection systems are still challenging for novelty detection algorithms.