portsentry and iptables

Fri Oct 26 17:20:54 EDT 2001

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