sshguard protects hosts from brute-force attacks against SSH and other services. It aggregates system logs and blocks repeat offenders using one of several firewall backends.
See the man pages in doc/ and the examples in examples/. This documentation can also be found online at http://www.sshguard.net/docs/.
See INSTALL.rst. Briefly, if you are building from Git:
autoreconf -i ./configure make && make install
./configure make && make install
sshguard is available under the terms of the OpenBSD license, which is based on the ISC License. See COPYING for details.