OpenSSL - OpenSSL is a free and open source software cryptography library that implements both the Secure Sockets Layer (SSL) and the Transport Layer Security (TLS) protocols, which are primarily used to provide secure communications between web browsers and …
Fail2ban - Intrusion prevention framework
Let's Encrypt - Let’s Encrypt is a free, automated, and open certificate authority brought to you by the Internet Security Research Group (ISRG).
RdpGuard - RdpGuard allows you to protect your Remote Desktop (RDP), POP3, FTP, SMTP, IMAP, MSSQL, MySQL, VoIP/SIP from brute-force attacks by blocking attacker's IP address. Fail2Ban for Windows.
Authy - Best rated Two-Factor Authentication smartphone app for consumers, simplest 2fa Rest API for developers and a strong authentication platform for the enterprise.
SSHGuard - SSHGuard monitors services through their logging activity.