Ubuntu Manpage: sshguard - block brute-force attacks by aggregating system logs

NAME

       sshguard - block brute-force attacks by aggregating system logs

SYNOPSIS

       sshguard   [-hv]   [-a   threshold]   [-b  threshold:blacklist_file]  [-i  pidfile]  [-p  blocktime]  [-s
       detection_time] [-w address | whitelist_file] [file ...]

DESCRIPTION

       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.

       sshguard  can  monitor  log  files  and  the standard output of running a shell command. Log messages are
       parsed line-by-line for recognized attack patterns.  Attackers are blocked when  enough  attack  patterns
       are  detected  in  a  configurable  time  interval.  Attackers  are  blocked  temporarily but can also be
       permanently blocked using the blacklist option.

       sshguard must be configured before its first run. See sshguard-setup(7).

OPTIONS

-a threshold (default 30)
Each detected attack increases an attacker's attack score, usually by 10. Block attackers when
their attack score exceeds threshold.

-b threshold:blacklist_file
Blacklist an attacker when its attack score exceeds threshold. Blacklisted addresses are written
to blacklist-file and never unblocked, even after restarting sshguard.

-i pidfile
Write the PID of sshguard to pidfile. pidfile is removed when sshguard exits.

-p blocktime (default 120)
Block first-time attackers for blocktime seconds. Subsequent blocks increase in duration by a
factor of 1.5. Since sshguard unblocks attackers at random intervals, actual block times may be
somewhat longer.

-s detection_time (default 1800)
Reset an attacker's attack score after detection_time seconds since the last attack. This means
that attackers who attack every detection_time seconds are never blocked by sshguard. However, an
increased detection_time may have an impact on legitimate users.

[-w address | whitelist_file]
Whitelist a single address, hostname, or address block given as address. This option can be given
multiple times. Alternatively, provide an absolute path to a whitelist_file containing addresses
to whitelist. See WHITELISTING.

-h Print usage information and exit.

-v Print version information and exit.

ENVIRONMENT

       SSHGUARD_DEBUG
              Set to enable verbose output from sshg-blocker.

FILES

       %PREFIX%/etc/sshguard.conf
              See sample configuration file.

WHITELISTING

       Whitelisted addresses are never blocked. Addresses can be specified on the command line or be stored in a
       file.

       On the command line, give the -w option one or more times with an IP  address,  CIDR  address  block,  or
       hostname  as  an  argument.  Hostnames  are  resolved once at startup. If a hostname resolves to multiple
       addresses, all of them are whitelisted. For example:

          sshguard -w 192.168.1.10 -w 192.168.0.0/24 -w friend.example.com
              -w 2001:0db8:85a3:0000:0000:8a2e:0370:7334
              -w 2002:836b:4179::836b:0000/126

       If the argument to -w begins with a forward slash ('/') or dot ('.'), the argument is treated as the path
       to a whitelist file.

       The whitelist file contains comments (lines beginning with '#'), addresses, address blocks, or hostnames,
       one per line.