Free tcp connections limit software for linux

TCPreen is a simple tool to monitor and analyze data transmitted between clients and servers through connection-oriented streams data such as a TCP sessions; it supports TCP over either IPv4 or IPv6. This tool focuses on the data stream (software/socket layer), not on the lower level transmission protocol as packet sniffers do.
TCPreen listens on a TCP port and wait for incoming connections to come in. Then, it forwards data sent by the connecting client to another server port (possibly on another computer) and forwards server responses back to the client.
TCPreen can display data on your console in real-time and/or save it to log files for later reference.There are various display formats.
While it was originally meant to help developers reverse-engineer TCP-based protocols, it can also be very useful to debug network server or client software or for a system administrator to monitor a TCP service.
Enhancements:
- libsolve/getaddrinfo.{c,h}, src/winstub.{c,h}:
- dirty kludge to resolve getaddrinfo & co at run-time
- so that tcpreen can still run on Windows 2000 and older.

TCP Knocking provides a port knocking implementation.
Often a secure system needs a port open so that only authorized persons can access a particular service and also the service should not exposed to attackers and worms that may use vulnerabilities that exist in the listening server. Port knocking is designed to be used as a complementary service to the existing authentication mechanism. But one of the biggest problems with port knocking is manipulating the firewall with timeouts.
When the correct knock sequence is sent, the firewall is modified for couple of seconds. Having the firewall open automatically for a time period will make any system administrator uncomfortable. TCP knocking attempts to solve the problem by incorporating the knock into the TCP handshake. Tcp knocking is similar to port knocking, but instead sending UDP packets with secret ports, the TCP handshake packets must include secrete codes. It is at least as secure as port knocking and it can be made secure with more hardening.
Modified TCP handshake:
In normal TCP handshake, the client sends the syn packet and chooses a random initial sequence number. The server responds with a packet that has both syn and ack flags set, choosing a random
The modified TCP handshake uses the empty fields in the header. The server does not respond to connection requests without a special code generated along with the syn packet. The server also encrypts the ISN in the ack packet (2) and the final packet of the three-way handshake must have the correct acknowledgment for the servers ISN. The system is further protected from brute-force attacks by closing the connection if the first attempt for the third packet does not have the expected acknowledgment sequence.
Also, rather than use conventional encryption techniques like HMAC for verification, this system uses a file with random numbers as the key. This is because of the limited unused space available in the TCP/IP header which makes HMAC very weak. By using a shared file, the length of the key can be much greater than traditional systems and even though some parts of the key can be revealed by attacks, the server can protect itself from replay attacks.
The handshake:
1) Syn
The syn packet does not use the 32 bit acknowledgment field in the TCP header as it the the first packet to initiate the connection. Further the 16 bit IPID can be used to transmit information. In the current implementation only the 32 bit acknowledgment field is used. Currently the 32 bit ack is derived from a 64 KB file which contains random numbers. The ISN and the source IP address along with the random numbers are used to generate this value.
2) Syn/Ack
The ISN is encrypted using the random numbers from the 64 KB file using the destination IP address as well as a 16 bit random number used as IPID. I do not have code for this part yet.
3) Ack
The client decrypts the syn number from the encrypted syn, the key file, the 16 bit IPID and its own IP address and sends the ack packet. The server closes all connections from the client for couple of minutes if it sends a wrong ack value. Part of the security relies on the fact that the ISN generated by Linux 2.6 is fairly random.
Implementation:
I have implemented only the first part, which is the server expecting secret code along with the first syn packet from the client. Hence it is very possible to brute-force the server. Also the system is designed with the second phase in mind, which is the encrypted Initial Sequence Number in the ack packet and closing the connection if the correct ack is not sent on the first try. I do not have an implementation for that yet. The security will be increased greatly when the second phase is incorporated. Also the ability to detect brute-force attacks can be added to this system.
But the current system can be used for protecting the server from worms and random scanning. The use-case is similar to port knocking but it does not use the ugly system of opening the firewall for a couple of seconds. Vanilla port knocking is susceptible to brute-force attacks as well. Besides, inserting a kernel module to just ssh into your server will increase your mad sysadmin points.
Enhancements:
- TCP knocking with Phase 1 of the protocol was implemented.

shd-tcp-tools project consists of TCP port forwarding, load balancing, rate control, and proxy tools.
shd-tcp-tools is a set of TCP network tools that supports port forwarding, network load balancing, rate limiting, and running servers behind firewalls. tcp-pf, listentwo, and connecttwo are port forwarding tools.
tcppipe is a one-directional TCP pipe that can be used as a substitute for one-directional netcat transfers, but with load balancing and rate control support.
tcp-pf can be used to forward a port from one host to another with load balancing and rate control support.
network load balancing scheme means using an interface or destination host based on past transfer history.
The listentwo and connecttwo tools can be used to run servers inside firewalled networks through third party TCP proxies.
Enhancements:
- Implemented tcppipe tool which replaces netcat when used as one-way tcp pipe.
- tcppipe supports load balancing and bandwidth rate control.
- tcppipe-least tool can be used to manipulate and show host files safely (it uses locking).

SQL::Abstract::Limit is a portable LIMIT emulation.

SYNOPSIS

use SQL::Abstract::Limit;

my $sql = SQL::Abstract::Limit->new( limit_dialect => LimitOffset );;

# or autodetect from a DBI $dbh:
my $sql = SQL::Abstract::Limit->new( limit_dialect => $dbh );

# or from a Class::DBI class:
my $sql = SQL::Abstract::Limit->new( limit_dialect => My::CDBI::App );

# or object:
my $obj = My::CDBI::App->retrieve( $id );
my $sql = SQL::Abstract::Limit->new( limit_dialect => $obj );

# generate SQL:
my ( $stmt, @bind ) = $sql->select( $table, @fields, %where, @order, $limit, $offset );

# Then, use these in your DBI statements
my $sth = $dbh->prepare( $stmt );
$sth->execute( @bind );

# Just generate the WHERE clause (only available for some syntaxes)
my ( $stmt, @bind ) = $sql->where( %where, @order, $limit, $offset );

UTIN Firewall script project is a script for Linux 2.4.x and iptables.

###########
# Configuration options, these will speed you up getting this script to
# work with your own setup.

#
# your LANs IP range and localhost IP. /24 means to only use the first 24
# bits of the 32 bit IP adress. the same as netmask 255.255.255.0
#
# INET_IP is used by me to allow myself to do anything to myself, might
# be a security risc but sometimes I want this. If you dont have a static
# IP, I suggest not using this option at all for now but its still
# enabled per default and will add some really nifty security bugs for all
# those who skips reading the documentation=)

LAN_IP="192.168.0.2"
LAN_BCAST_ADRESS="192.168.0.255"
LAN_IFACE="eth1"

LO_IFACE="lo"
LO_IP="127.0.0.1"

INET_IP="194.236.50.155"
INET_IFACE="eth0"

IPTABLES="/usr/local/sbin/iptables"

#########
# Load all required IPTables modules
#

#
# Needed to initially load modules
#
/sbin/depmod -a

#
# Adds some iptables targets like LOG, REJECT and MASQUARADE.
#
/sbin/modprobe ipt_LOG
#/sbin/modprobe ipt_REJECT
/sbin/modprobe ipt_MASQUERADE

#
# Support for owner matching
#
#/sbin/modprobe ipt_owner

#
# Support for connection tracking of FTP and IRC.
#
#/sbin/modprobe ip_conntrack_ftp
#/sbin/modprobe ip_conntrack_irc

#
# Enable ip_forward, this is critical since it is turned off as defaul in
# Linux.
#

echo "1" > /proc/sys/net/ipv4/ip_forward

#
# Dynamic IP users:
#
#echo "1" > /proc/sys/net/ipv4/ip_dynaddr

#
# Enable simple IP Forwarding and Network Address Translation
#

$IPTABLES -t nat -A POSTROUTING -o $INET_IFACE -j SNAT --to-source $INET_IP

#
# Set default policies for the INPUT, FORWARD and OUTPUT chains
#

$IPTABLES -P INPUT DROP
$IPTABLES -P OUTPUT DROP
$IPTABLES -P FORWARD DROP

#
# bad_tcp_packets chain
#
# Take care of bad TCP packets that we dont want.
#

$IPTABLES -N bad_tcp_packets
$IPTABLES -A bad_tcp_packets -p tcp ! --syn -m state --state NEW -j LOG
--log-prefix "New not syn:"
$IPTABLES -A bad_tcp_packets -p tcp ! --syn -m state --state NEW -j DROP

#
# Do some checks for obviously spoofed IPs
#

$IPTABLES -A bad_tcp_packets -i $INET_IFACE -s 192.168.0.0/16 -j DROP
$IPTABLES -A bad_tcp_packets -i $INET_IFACE -s 10.0.0.0/8 -j DROP
$IPTABLES -A bad_tcp_packets -i $INET_IFACE -s 172.16.0.0/12 -j DROP
$IPTABLES -A bad_tcp_packets -i $LAN_IFACE ! -s 192.168.0.0/16 -j DROP

#
# Bad TCP packets we dont want
#

$IPTABLES -A FORWARD -p tcp -j bad_tcp_packets

#
# Accept the packets we actually want to forward between interfaces.
#

$IPTABLES -A FORWARD -p tcp --dport 21 -i $LAN_IFACE -j ACCEPT
$IPTABLES -A FORWARD -p tcp --dport 80 -i $LAN_IFACE -j ACCEPT
$IPTABLES -A FORWARD -p tcp --dport 110 -i $LAN_IFACE -j ACCEPT

$IPTABLES -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
$IPTABLES -A FORWARD -m limit --limit 3/minute --limit-burst 3 -j LOG
--log-level DEBUG --log-prefix "IPT FORWARD packet died: "


#
# Create separate chains for ICMP, TCP and UDP to traverse
#

$IPTABLES -N icmp_packets
$IPTABLES -N tcp_packets
$IPTABLES -N udpincoming_packets

#
# The allowed chain for TCP connections
#

$IPTABLES -N allowed
$IPTABLES -A allowed -p TCP --syn -j ACCEPT
$IPTABLES -A allowed -p TCP -m state --state ESTABLISHED,RELATED
-j ACCEPT
$IPTABLES -A allowed -p TCP -j DROP

#
# ICMP rules
#

# Changed rules totally
$IPTABLES -A icmp_packets -p ICMP -s 0/0 --icmp-type 8 -j ACCEPT
$IPTABLES -A icmp_packets -p ICMP -s 0/0 --icmp-type 11 -j ACCEPT

#
# TCP rules
#

$IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 21 -j allowed
$IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 22 -j allowed
$IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 80 -j allowed
$IPTABLES -A tcp_packets -p TCP -s 0/0 --dport 113 -j allowed

#
# UDP ports
#

$IPTABLES -A udpincoming_packets -p UDP -s 0/0 --source-port 53 -j ACCEPT
$IPTABLES -A udpincoming_packets -p UDP -s 0/0 --source-port 123 -j ACCEPT
$IPTABLES -A udpincoming_packets -p UDP -s 0/0 --source-port 2074 -j ACCEPT
$IPTABLES -A udpincoming_packets -p UDP -s 0/0 --source-port 4000 -j ACCEPT

#
# INPUT chain
#
# Bad TCP packets we dont want
#

$IPTABLES -A INPUT -p tcp -j bad_tcp_packets

#
# Rules for incoming packets from anywhere
#

$IPTABLES -A INPUT -p ICMP -j icmp_packets
$IPTABLES -A INPUT -p TCP -j tcp_packets
$IPTABLES -A INPUT -p UDP -j udpincoming_packets

#
# Rules for special networks not part of the Internet
#

$IPTABLES -A INPUT -p ALL -i $LO_IFACE -s $LO_IP -j ACCEPT
$IPTABLES -A INPUT -p ALL -i $LO_IFACE -s $LAN_IP -j ACCEPT
$IPTABLES -A INPUT -p ALL -i $LO_IFACE -s $INET_IP -j ACCEPT
$IPTABLES -A INPUT -p ALL -d $INET_IP -m state --state ESTABLISHED,RELATED
-j ACCEPT
$IPTABLES -A INPUT -m limit --limit 3/minute --limit-burst 3
-j LOG --log-level DEBUG --log-prefix "IPT INPUT packet died: "

#
# OUTPUT chain
#
#
# Bad TCP packets we dont want
#

$IPTABLES -A OUTPUT -p tcp -j bad_tcp_packets


$IPTABLES -A OUTPUT -p ALL -s $LO_IP -j ACCEPT
$IPTABLES -A OUTPUT -p ALL -s $LAN_IP -j ACCEPT
$IPTABLES -A OUTPUT -p ALL -s $INET_IP -j ACCEPT
$IPTABLES -A OUTPUT -m limit --limit 3/minute --limit-burst 3
-j LOG --log-level DEBUG --log-prefix "IPT OUTPUT packet died: "

Just For Fun Network Management System is a PHP-based network management system that features an integrated syslog, Tacacs, TFTP configuration downloading, SNMP polling, SNMP traps, journalling, auto-discovery, performance graphs (RRD), SLAs, and a lot more.
Just For Fun Network Management System uses MySQL or PostgreSQL as the backend and works under Linux and Windows.
Main features:
- Written in PHP4 (works in PHP5 too)
- Fully tested on Linux, FreeBSD and Win2K
- Should work on any other system which supports PHP
- PHP/cron scripts for polling, analizing and consolidating data
- Database Backend MySQL or PostgreSQL
- Configurable Event Types and Severity Levels
- Modular and Extensible
- Advanced Event Filter
- Interface Autodiscovery
- Licensed under the GNU GPL
- Event Console, Shows Events / Tacacs / Syslog / Alarms in the same time-ordered display
- Map & Sub-Map support
- Graphical Interface Traffic, Round Trip Time, Packet Loss Monitoring, and a LOT more
- Variable Time Span in the graphs
- Total Administration via web
- Sound Alerts in your browser
- Events RDF Feed (for newstickers)
- Works with HTTPS
- Traffic Bytes
- Utilization %
- Packets per Second, Errors per Second, Error Rate
- Round Trip Time and Packet Loss (Cisco & Smokeping)
- Drops
- TCP Connections: Incoming, Outgoing, Established, Delay
- Number of Processes, Number of Users
- Used Memory and Disks with Aggregation
- Processor Utilization and Load Average
- Temperature
- Interfaces (Network cards)
- Host (Processor, Load Average)
- Storage (Disks and Memory)
- Applications Running (HostMIB)
- Cisco Ping (RTT & PL on Cisco)
- BGP4 (BGP sessions status)
- TCP (TCP Connections, Delay)
- Cisco MAC Accounting
- Cisco IP Accounting
- Cisco CSS
- Cisco SA Agent
- Cisco Enviormental (Temperature, Voltage, etc)
- Internet Information Server (IIS) MIB
- Livingstone PortMaster3 Serial Line MIB
- Compaq Insight Manager MIB (Disk, Fan and Temperature)
- Apache /server-status monitoring
- TCP Port Content Regexp Checking (or URL)
- Configurable per Circuit SLAs (with RPN logic)
- Internal Authorization Framework
- Per Event Journals and Acknowledge
- Triggers / Actions Framework for email/others alerts.
- Database Abstraction Framework
- CSV Export
- Distributed Polling
- Object Oriented
- Consistent API
Enhancements:
- Better support for PHP 5 and RRDTool 1.2.x, OS/400 integration, Dell Chassis alarm monitoring, and fixes for all reported issues.

Configuration with no services supported script is for a single host firewall configuration with no services supported by the firewall machine itself.

Sample:

# USER CONFIGURABLE SECTION

# The name and location of the ipchains utility.
IPTABLES=iptables

# The path to the ipchains executable.
PATH="/usr/local/sbin"

# Our internal network address space and its supporting network device.
OURNET="10.5.0.0/24"
OURBCAST="10.5.0.255"
OURDEV="eth0"

# The outside address and the network device that supports it.
ANYADDR="0/0"
ANYDEV="ppp0"

# The TCP services we wish to allow to pass - "" empty means all ports
# note: comma separated
TCPIN="ssh,ftp,ftp-data"
TCPOUT="smtp,www,ssh,telnet,ftp,ftp-data,irc,http"

# The UDP services we wish to allow to pass - "" empty means all ports
# note: comma separated
UDPIN="domain"
UDPOUT="domain"

# The ICMP services we wish to allow to pass - "" empty means all types
# ref: /usr/include/netinet/ip_icmp.h for type numbers
# note: comma separated
ICMPIN="0,3,11"
ICMPOUT="8,3,11"

# Logging; uncomment the following line to enable logging of datagrams
# that are blocked by the firewall.
# LOGGING=1

# END USER CONFIGURABLE SECTION
####################################
# Flush the Input table rules
echo -n Flushing forward... && {
$IPTABLES -F FORWARD
} && echo done

# We want to deny incoming access by default.
# echo -n Denying incoming access... && {
# $IPTABLES -P FORWARD drop
# } && echo done

# Drop all datagrams destined for this host received from outside.
echo -n Dropping incoming datagrams... && {
$IPTABLES -A INPUT -i $ANYDEV -j DROP
} && echo done

# SPOOFING
# We should not accept any datagrams with a source address matching ours
# from the outside, so we deny them.
echo -n Preventing spoofing... && {
$IPTABLES -A FORWARD -s $OURNET -i $ANYDEV -j DROP
} && echo done

# SMURF
# Disallow ICMP to our broadcast address to prevent "Smurf" style attack.
echo -n Preventing SMURFs... && {
$IPTABLES -A FORWARD -p icmp -i $ANYDEV -d $OURNET -j DROP
} && echo done

# We should accept fragments, in iptables we must do this explicitly.
echo -n Accepting fragments... && {
$IPTABLES -A FORWARD -f -j ACCEPT
} && echo done

# TCP
# We will accept all TCP datagrams belonging to an existing connection
# (i.e. having the ACK bit set) for the TCP ports were allowing through.
# This should catch more than 95 % of all valid TCP packets.
echo -n Accepting valid incoming tcp datagrams on existing connections... && {
$IPTABLES -A FORWARD -m multiport -p tcp -d $OURNET --dports $TCPIN ! --tcp-flags SYN,ACK ACK -j ACCEPT
} && echo done
echo -n Accepting valid outgoing tcp datagrams on existing connections... && {
$IPTABLES -A FORWARD -m multiport -p tcp -s $OURNET --sports $TCPIN ! --tcp-flags SYN,ACK ACK -j ACCEPT
} && echo done

# TCP - INCOMING CONNECTIONS
# We will accept connection requests from the outside only on the
# allowed TCP ports.
echo -n Accepting incoming tcp connections on allowed ports... && {
$IPTABLES -A FORWARD -m multiport -p tcp -i $ANYDEV -d $OURNET --dports $TCPIN --syn -j ACCEPT
} && echo done

# TCP - OUTGOING CONNECTIONS
# We will accept all outgoing tcp connection requests on the allowed TCP ports.
echo -n Accepting outgoing traffic on allowed tcp ports... && {
$IPTABLES -A FORWARD -m multiport -p tcp -i $OURDEV -d $ANYADDR --dports $TCPOUT --syn -j ACCEPT
} && echo done

# UDP - INCOMING
# allow UDP datagrams in on the allowed ports and back.
echo -n Allowing UDP datagrams in on the allowed ports and back... && {
$IPTABLES -A FORWARD -m multiport -p udp -i $ANYDEV -d $OURNET --dports $UDPIN -j ACCEPT
$IPTABLES -A FORWARD -m multiport -p udp -i $ANYDEV -s $OURNET --sports $UDPIN -j ACCEPT
} && echo done

# UDP - OUTGOING
# We will allow UDP datagrams out to the allowed ports and back.
echo -n Allowing UDP datagrams out on the allowed ports and back... && {
$IPTABLES -A FORWARD -m multiport -p udp -i $OURDEV -d $ANYADDR --dports $UDPOUT -j ACCEPT
$IPTABLES -A FORWARD -m multiport -p udp -i $OURDEV -s $ANYADDR --sports $UDPOUT -j ACCEPT
} && echo done

# ICMP - INCOMING
# We will allow ICMP datagrams in of the allowed types.
# echo -n Allowing ICMP datagrams in of the allowed types... && {
# $IPTABLES -A FORWARD -p icmp -i $ANYDEV -d $OURNET --icmp-type $ICMPIN -j ACCEPT
# } && echo done

# ICMP - OUTGOING
# We will allow ICMP datagrams out of the allowed types.
# echo -n Allowing ICMP datagrams out of the allowed types... && {
# $IPTABLES -A FORWARD -p icmp -i $OURDEV -d $ANYADDR --icmp-type $ICMPOUT -j ACCEPT
# } && echo done

# DEFAULT and LOGGING
# All remaining datagrams fall through to the default
# rule and are dropped. They will be logged if youve
# configured the LOGGING variable above.
#

# DoS
# enabling Syn-flood protection
echo -n Enabling Syn-flood protection... && {
iptables -A FORWARD -p tcp --syn -m limit --limit 1/s -j ACCEPT
} && echo done
# Enabling Furtive port scanner protection
echo -n Enabling Furtive port scanner protection... && {
iptables -A FORWARD -p tcp --tcp-flags SYN,ACK,FIN,RST RST -m limit --limit 1/s -j ACCEPT
} && echo done
# Enabling ping of death protection
echo -n Enabling ping of death protection... && {
iptables -A FORWARD -p icmp --icmp-type echo-request -m limit --limit 1/s -j ACCEPT
} && echo done


if [ "$LOGGING" ]
then
# Log barred TCP
$IPTABLES -A FORWARD -m tcp -p tcp -j LOG
# Log barred UDP
$IPTABLES -A FORWARD -m udp -p udp -j LOG
# Log barred ICMP
$IPTABLES -A FORWARD -m udp -p icmp -j LOG
fi
#
# end.