portsentry and iptables

Fri Oct 26 17:26:19 EDT 2001

that's just it, I'm having trouble understanding the configuration file.
I've read that and the readme, but  not really understanding it.

On 26 Oct 2001, John Covici wrote:

> The only iptables specific thing you have to do with portsentry is to
> uncomment the kill_route line specific to iptables -- changing the
> path if necessary.  Other questions may revolve around portsentry in
> general and for those you have to consult your /etc/services file and
> decide what you want to do with your system -- do you have a web
> server, mail server, etc.
> 
> on Wed, 24 Oct 2001 22:53:16 -0400 (EDT) Deedra Waters <dmwaters at tampabay.rr.com> wrote:
> 
> > I've read  the documentation for portsentry, but am having a lot of
> > trouble getting it going. my main problems are with the portsentry.conf
> > fileI'm really confused as to how to get it going, and working correctly
> > with the iptables I have set up... if someone could help me with this I'd
> > appreciate it... I'm attaching the portsentry.conf file to this message...
> > 
> > Like I said, I've read the readme files and the portsentry.conf file
> > itself, but am still really confused as to how to set it up and what to
> > comment and uncomment in it.
> > and what to change.
> > 
> > # PortSentry Configuration
> > #
> > # $Id: portsentry.conf,v 1.23 2001/06/26 15:20:56 crowland Exp crowland $
> > #
> > # IMPORTANT NOTE: You CAN NOT put spaces between your port arguments.
> > # 
> > # The default ports will catch a large number of common probes
> > #
> > # All entries must be in quotes.
> > 
> > 
> > #######################
> > # Port Configurations #
> > #######################
> > #
> > #
> > # Some example port configs for classic and basic Stealth modes
> > #
> > # I like to always keep some ports at the "low" end of the spectrum.
> > # This will detect a sequential port sweep really quickly and usually
> > # these ports are not in use (i.e. tcpmux port 1)
> > #
> > # ** X-Windows Users **: If you are running X on your box, you need to be sure
> > # you are not binding PortSentry to port 6000 (or port 2000 for OpenWindows users). 
> > # Doing so will prevent the X-client from starting properly. 
> > #
> > # These port bindings are *ignored* for Advanced Stealth Scan Detection Mode.
> > #
> > 
> > # Un-comment these if you are really anal:
> > #TCP_PORTS="1,7,9,11,15,70,79,80,109,110,111,119,138,139,143,512,513,514,515,540,635,1080,1524,2000,2001,4000,4001,5742,6000,6001,6667,12345,12346,20034,27665,30303,32771,32772,32773,32774,31337,40421,40425,49724,54320"
> > #UDP_PORTS="1,7,9,66,67,68,69,111,137,138,161,162,474,513,517,518,635,640,641,666,700,2049,31335,27444,34555,32770,32771,32772,32773,32774,31337,54321"
> > #
> > # Use these if you just want to be aware:
> > TCP_PORTS="1,11,15,79,111,119,143,540,635,1080,1524,2000,5742,6667,12345,12346,20034,27665,31337,32771,32772,32773,32774,40421,49724,54320"
> > UDP_PORTS="1,7,9,69,161,162,513,635,640,641,700,37444,34555,31335,32770,32771,32772,32773,32774,31337,54321"
> > #
> > # Use these for just bare-bones
> > #TCP_PORTS="1,11,15,110,111,143,540,635,1080,1524,2000,12345,12346,20034,32771,32772,32773,32774,49724,54320"
> > #UDP_PORTS="1,7,9,69,161,162,513,640,700,32770,32771,32772,32773,32774,31337,54321"
> > 
> > ###########################################
> > # Advanced Stealth Scan Detection Options #
> > ###########################################
> > #
> > # This is the number of ports you want PortSentry to monitor in Advanced mode.
> > # Any port *below* this number will be monitored. Right now it watches 
> > # everything below 1024. 
> > # 
> > # On many Linux systems you cannot bind above port 61000. This is because
> > # these ports are used as part of IP masquerading. I don't recommend you
> > # bind over this number of ports. Realistically: I DON'T RECOMMEND YOU MONITOR 
> > # OVER 1024 PORTS AS YOUR FALSE ALARM RATE WILL ALMOST CERTAINLY RISE. You've been
> > # warned! Don't write me if you have have a problem because I'll only tell
> > # you to RTFM and don't run above the first 1024 ports.
> > #
> > #
> > ADVANCED_PORTS_TCP="1024"
> > ADVANCED_PORTS_UDP="1024"
> > #
> > # This field tells PortSentry what ports (besides listening daemons) to
> > # ignore. This is helpful for services like ident that services such 
> > # as FTP, SMTP, and wrappers look for but you may not run (and probably 
> > # *shouldn't* IMHO). 
> > #
> > # By specifying ports here PortSentry will simply not respond to
> > # incoming requests, in effect PortSentry treats them as if they are
> > # actual bound daemons. The default ports are ones reported as 
> > # problematic false alarms and should probably be left alone for
> > # all but the most isolated systems/networks.
> > #
> > # Default TCP ident and NetBIOS service
> > ADVANCED_EXCLUDE_TCP="113,139"
> > # Default UDP route (RIP), NetBIOS, bootp broadcasts.
> > ADVANCED_EXCLUDE_UDP="520,138,137,67"
> > 
> > 
> > ######################
> > # Configuration Files#
> > ######################
> > #
> > # Hosts to ignore
> > IGNORE_FILE="/usr/local/psionic/portsentry/portsentry.ignore"
> > # Hosts that have been denied (running history)
> > HISTORY_FILE="/usr/local/psionic/portsentry/portsentry.history"
> > # Hosts that have been denied this session only (temporary until next restart)
> > BLOCKED_FILE="/usr/local/psionic/portsentry/portsentry.blocked"
> > 
> > ##############################
> > # Misc. Configuration Options#
> > ##############################
> > #
> > # DNS Name resolution - Setting this to "1" will turn on DNS lookups
> > # for attacking hosts. Setting it to "0" (or any other value) will shut
> > # it off.
> > RESOLVE_HOST = "1"
> > 
> > ###################
> > # Response Options#
> > ###################
> > # Options to dispose of attacker. Each is an action that will 
> > # be run if an attack is detected. If you don't want a particular
> > # option then comment it out and it will be skipped.
> > #
> > # The variable $TARGET$ will be substituted with the target attacking
> > # host when an attack is detected. The variable $PORT$ will be substituted
> > # with the port that was scanned. 
> > #
> > ##################
> > # Ignore Options #
> > ##################
> > # These options allow you to enable automatic response
> > # options for UDP/TCP. This is useful if you just want
> > # warnings for connections, but don't want to react for  
> > # a particular protocol (i.e. you want to block TCP, but
> > # not UDP). To prevent a possible Denial of service attack
> > # against UDP and stealth scan detection for TCP, you may 
> > # want to disable blocking, but leave the warning enabled. 
> > # I personally would wait for this to become a problem before
> > # doing though as most attackers really aren't doing this.
> > # The third option allows you to run just the external command
> > # in case of a scan to have a pager script or such execute
> > # but not drop the route. This may be useful for some admins
> > # who want to block TCP, but only want pager/e-mail warnings
> > # on UDP, etc.
> > #
> > # 
> > # 0 = Do not block UDP/TCP scans.
> > # 1 = Block UDP/TCP scans.
> > # 2 = Run external command only (KILL_RUN_CMD)
> > 
> > BLOCK_UDP="1"
> > BLOCK_TCP="1"
> > 
> > ###################
> > # Dropping Routes:#
> > ###################
> > # This command is used to drop the route or add the host into
> > # a local filter table. 
> > #
> > # The gateway (333.444.555.666) should ideally be a dead host on 
> > # the *local* subnet. On some hosts you can also point this at
> > # localhost (127.0.0.1) and get the same effect. NOTE THAT
> > # 333.444.555.66 WILL *NOT* WORK. YOU NEED TO CHANGE IT!!
> > #
> > # ALL KILL ROUTE OPTIONS ARE COMMENTED OUT INITIALLY. Make sure you
> > # uncomment the correct line for your OS. If you OS is not listed
> > # here and you have a route drop command that works then please
> > # mail it to me so I can include it. ONLY ONE KILL_ROUTE OPTION
> > # CAN BE USED AT A TIME SO DON'T UNCOMMENT MULTIPLE LINES.
> > #
> > # NOTE: The route commands are the least optimal way of blocking
> > # and do not provide complete protection against UDP attacks and
> > # will still generate alarms for both UDP and stealth scans. I
> > # always recommend you use a packet filter because they are made
> > # for this purpose.
> > #
> > 
> > # Generic 
> > #KILL_ROUTE="/sbin/route add $TARGET$ 333.444.555.666"
> > 
> > # Generic Linux 
> > #KILL_ROUTE="/sbin/route add -host $TARGET$ gw 333.444.555.666"
> > 
> > # Newer versions of Linux support the reject flag now. This 
> > # is cleaner than the above option.
> > #KILL_ROUTE="/sbin/route add -host $TARGET$ reject"
> > 
> > # Generic BSD (BSDI, OpenBSD, NetBSD, FreeBSD)
> > #KILL_ROUTE="/sbin/route add $TARGET$ 333.444.555.666"
> > 
> > # Generic Sun 
> > #KILL_ROUTE="/usr/sbin/route add $TARGET$ 333.444.555.666 1"
> > 
> > # NEXTSTEP
> > #KILL_ROUTE="/usr/etc/route add $TARGET$ 127.0.0.1 1"
> > 
> > # FreeBSD
> > #KILL_ROUTE="route add -net $TARGET$ -netmask 255.255.255.255 127.0.0.1 -blackhole"
> > 
> > # Digital UNIX 4.0D (OSF/1 / Compaq Tru64 UNIX)
> > #KILL_ROUTE="/sbin/route add -host -blackhole $TARGET$ 127.0.0.1"
> > 
> > # Generic HP-UX
> > #KILL_ROUTE="/usr/sbin/route add net $TARGET$ netmask 255.255.255.0 127.0.0.1"
> > 
> > ##
> > # Using a packet filter is the PREFERRED. The below lines
> > # work well on many OS's. Remember, you can only uncomment *one*
> > # KILL_ROUTE option.
> > ##
> > 
> > # ipfwadm support for Linux
> > #KILL_ROUTE="/sbin/ipfwadm -I -i deny -S $TARGET$ -o"
> > #
> > # ipfwadm support for Linux (no logging of denied packets)
> > #KILL_ROUTE="/sbin/ipfwadm -I -i deny -S $TARGET$"
> > #
> > # ipchain support for Linux
> > #KILL_ROUTE="/sbin/ipchains -I input -s $TARGET$ -j DENY -l"
> > #
> > # ipchain support for Linux (no logging of denied packets)
> > #KILL_ROUTE="/sbin/ipchains -I input -s $TARGET$ -j DENY"
> > #
> > # iptables support for Linux
> > #KILL_ROUTE="/usr/local/bin/iptables -I INPUT -s $TARGET$ -j DROP"
> > #
> > # For those of you running FreeBSD (and compatible) you can
> > # use their built in firewalling as well. 
> > #
> > #KILL_ROUTE="/sbin/ipfw add 1 deny all from $TARGET$:255.255.255.255 to any"
> > #
> > #
> > # For those running ipfilt (OpenBSD, etc.)
> > # NOTE THAT YOU NEED TO CHANGE external_interface TO A VALID INTERFACE!!
> > #
> > #KILL_ROUTE="/bin/echo 'block in log on external_interface from $TARGET$/32 to any' | /sbin/ipf -f -"
> > 
> > 
> > ###############
> > # TCP Wrappers#
> > ###############
> > # This text will be dropped into the hosts.deny file for wrappers
> > # to use. There are two formats for TCP wrappers:
> > #
> > # Format One: Old Style - The default when extended host processing
> > # options are not enabled.
> > #
> > KILL_HOSTS_DENY="ALL: $TARGET$"
> > 
> > # Format Two: New Style - The format used when extended option
> > # processing is enabled. You can drop in extended processing
> > # options, but be sure you escape all '%' symbols with a backslash
> > # to prevent problems writing out (i.e. \%c \%h )
> > #
> > #KILL_HOSTS_DENY="ALL: $TARGET$ : DENY"
> > 
> > ###################
> > # External Command#
> > ###################
> > # This is a command that is run when a host connects, it can be whatever
> > # you want it to be (pager, etc.). This command is executed before the 
> > # route is dropped or after depending on the KILL_RUN_CMD_FIRST option below
> > #
> > #
> > # I NEVER RECOMMEND YOU PUT IN RETALIATORY ACTIONS AGAINST THE HOST SCANNING 
> > # YOU!
> > #
> > # TCP/IP is an *unauthenticated protocol* and people can make scans appear out 
> > # of thin air. The only time it is reasonably safe (and I *never* think it is 
> > # reasonable) to run reverse probe scripts is when using the "classic" -tcp mode. 
> > # This mode requires a full connect and is very hard to spoof.
> > #
> > # The KILL_RUN_CMD_FIRST value should be set to "1" to force the command 
> > # to run *before* the blocking occurs and should be set to "0" to make the 
> > # command run *after* the blocking has occurred. 
> > #
> > #KILL_RUN_CMD_FIRST = "0"
> > #
> > #
> > #KILL_RUN_CMD="/some/path/here/script $TARGET$ $PORT$"
> > 
> > 
> > #####################
> > # Scan trigger value#
> > #####################
> > # Enter in the number of port connects you will allow before an 
> > # alarm is given. The default is 0 which will react immediately.
> > # A value of 1 or 2 will reduce false alarms. Anything higher is 
> > # probably not necessary. This value must always be specified, but
> > # generally can be left at 0. 
> > #
> > # NOTE: If you are using the advanced detection option you need to
> > # be careful that you don't make a hair trigger situation. Because
> > # Advanced mode will react for *any* host connecting to a non-used
> > # below your specified range, you have the opportunity to really 
> > # break things. (i.e someone innocently tries to connect to you via 
> > # SSL [TCP port 443] and you immediately block them). Some of you
> > # may even want this though. Just be careful.
> > #
> > SCAN_TRIGGER="0"
> > 
> > ######################
> > # Port Banner Section#
> > ######################
> > #
> > # Enter text in here you want displayed to a person tripping the PortSentry.
> > # I *don't* recommend taunting the person as this will aggravate them.
> > # Leave this commented out to disable the feature
> > #
> > # Stealth scan detection modes don't use this feature
> > #
> > #PORT_BANNER="** UNAUTHORIZED ACCESS PROHIBITED *** YOUR CONNECTION ATTEMPT HAS BEEN LOGGED. GO AWAY."
> > 
> > # EOF
> 
> -- 
>          John Covici
>          covici at ccs.covici.com
> 
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