The best free alternative to RdpGuard is Fail2ban, which is also Open Source. If that doesn't suit you, our users have ranked more than 10 alternatives to RdpGuard and nine of them is free so hopefully you can find a suitable replacement. Other interesting free alternatives to RdpGuard are SSHGuard, Cyberarms Intrusion Detection and Defense, Denyhosts and IPQ BDB.
Fail2ban scans log files (e.g. /var/log/apache/error_log) and bans IPs that show the malicious signs -- too many password failures, seeking for exploits, etc. Generally Fail2Ban is then used to update firewall rules to reject the IP addresses for a specified amount of time...
SSHGuard monitors services through their logging activity. It reacts to messages about dangerous activity by blocking the source address with the local firewall. SSHGuard employs a clever parser that can transparently recognize several logging formats at once (syslog, syslog-ng...
Out-of-the-box security for Remote Deskop, Exchange, OWA, SharePoint, CRM, generic IIS applications and many other server systems.
The idea of denying access to SSH servers is nothing new and I was inspired by many other scripts that I discovered. However, none of them did things the way I envisioned them to. Also, they were all shell scripts which do not offer the elegance of Python.
IPQ BDB filtering is done by a user space netfilter daemon that issues verdicts after looking up the IP address in a Berkeley DB. The fuzzy blocking model, freely inspired by STOCKADE, is designed to block non-distributed dictionary attacks and mitigate spam.
Monitor logs from several sources and execute actions based on some rules. Can be used to protect against brute-force attacks.
Protected against RDP-Brute forcers. It installs a service which scans the event log for anomalies every 30 seconds (by default).
Built to react fast in server farms environments (ISPs, HSPs, organisations...) Hookem-Banem is a log monitoring system which monitors logs being sent to a central server (syslog, file...) and on detection of malicious intent (repeated login failures, many failed RCPT commands...
win2ban is a Fail2ban implementation for Windows systems. It is a packaging of Fail2ban, Python, Cygwin, Winlogbeat and many other related tools to make it a complete and ready-to-use solution for brute-force attack protection.
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There is the chance to block an IP forever. It's completely free.