Denyhosts

Script to thwart ssh and imap attacks

DenyHosts is a utility developed by Phil Schwartz and maintained by a number of developers which aims to thwart sshd ssh server brute force attacks.

If you’ve ever looked at your ssh log /var/log/auth.log you may be alarmed to see how many hackers attempted to gain access to your server. Denyhosts helps you

• Parses /var/log/auth.log to find all login attempts
• Can be run from the command line, cron or as a daemon new in 0.9
• Records all failed login attempts for the user and offending host
• For each host that exceeds a threshold count, records the evil host
• Keeps track of each non-existent user eg. sdada when a login attempt failed.
• Keeps track of each existing user eg. root when a login attempt failed.
• Keeps track of each offending host hosts can be purged
• Keeps track of suspicious logins
• Keeps track of the file offset, so that you can reparse the same file
• When the log file is rotated, the script will detect it
• Appends /etc/hosts.allow
• Optionally sends an email of newly banned hosts and suspicious logins.
• Resolves IP addresses to hostnames, if you want