Jenkins is a simple, free and open-source Continuous Integration tool (CI), which is one of the most popular application development practices in recent times. Jenkins is widely used for building, deploying and automating any project, providing hundreds of different plugins. It supports version control tools, including AccuRev, Subversion, Git, CVS, Perforce, ClearCase, Mercurial, and RTC, and can execute Apache Ant, Apache Maven, and sbt based projects as well as arbitrary shell scripts.
OpenSSH is one of the most popular tools that uses SSH protocol for secure system administration, file transfers, and other communication across the Internet. It is free and used by system administrators to manage remote systems. OpenSSH runs on port 22 and it is the first target of a hacker. So you may need to harden your OpenSSH server to protect it from hackers.