Security patches in open-source software, providing security fixes to identified vulnerabilities, are crucial in protecting against cyberattacks. Despite the National Vulnerability Database (NVD) publishes identified vulnerabilities, a vast majority of vulnerabilities and their corresponding security patches remain beyond public exposure, e.g., in the open-source libraries that are heavily relied on by developers. An extensive security patches dataset could help end-users such as security companies, e.g., building a security knowledge base, or researchers, e.g., aiding in vulnerability research. To curate security patches including undisclosed patches at a large scale and low cost, we propose a deep neural-network-based approach built upon commits of open-source repositories. We build security patch datasets that include 38,291 security-related commits and 1,045 CVE patches from four C libraries. We manually verify each commit, among the 38,291 security-related commits, to determine if they are security-related. We devise a deep learning-based security patch identification system that consists of two neural networks: one commit-message neural network that utilizes pretrained word representations learned from our commits dataset; and one code-revision neural network that takes code before and after revision and learns the distinction on the statement level. Our evaluation results show that our system outperforms SVM and K-fold stacking algorithm, achieving as high as 87.93% F1-score and precision of 86.24%. We deployed our pipeline and learned model in an industrial production environment to evaluate the generalization ability of our approach. The industrial dataset consists of 298,917 commits from 410 new libraries that range from a wide functionality. Our experiment results and observation proved that our approach identifies security patches effectively among open-sourced projects.