Security :: Write A Specific Rule To Check For Spoofed Packets?
Apr 21, 2010
Just wanted input for this script i have cobbeled together. Its not done yet. I am trying to think of ways to close up my outgoing while maintaining full functionality of my laptop ( irc, web stuff, a torrent or two, etc.) . Anyways, I have done some myself; as well as, pulling bits and pieces from other stuff out on the web. I am starting to wonder why i have to write a specific rule to check for spoofed packets if my default input is set top drop. wouldnt it be caught?
Code:
#!/bin/bash
### Laptop + Desktop: No Forwarding firewall ip4 / ip6
### Distro > Debian / Ubuntu.
### oliverteasley@gmail.com
[Code]....
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Jan 3, 2011
how can i drop igmp port 0 packets with iptables rule? my log file is full of this router advertisement.
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Apr 5, 2011
My firewall , wich is an Ubuntu server 10.10 , have 3 interfaces:
eth0(192.168.0.254):linked to the DMZ
eth1(192.168.1.254):linked to the LAN
eth3(212.217.0.1):linked to the Internet
-The DMZ have one web server with a static address (192.168.0.1).
-My LAN address range is (192.168.1.2-192.168.1.100) managed by a DHCP server in the same firwall machine.
There are some of the rules that I need to set up :
-Allow HTTP between the LAN and the internet
-Allow HTTP between the web server in the DMZ, and the internet.
Is there a way to tell the firewall , to redirect all incoming HTTP requests only to the web server in the DMZ ?
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Aug 30, 2010
i need to write a program in c that can sniff packets from Ethernet and distinguish RTP packets from Non-RTP packets, i have no idea what should i do
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Jul 23, 2011
For example, can I write something to the effect: block all outbound UDP connections over port 53 except those going to IP 123.456.789. Or stated another way: Block outbound to port 53/udp NOT going to ip address 123.454.678Is it possible to do this? How would I write the argument?
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Oct 26, 2010
My IP is being spoofed by someone and I suspect it is being used for malicious purposes(possibly illegal ones). How can I stop someone from using my IP? I'm using a dynamic IP but obtaining a new IP seems to be useless. Changing my wireless password will probably just as useless I guess.
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Jul 16, 2010
Question (and Google results aren't making this clear): Ubuntu has both iptables & ip6tables installed. 1. If I set a rule in iptables, does that rule also apply to ipv6, or just ipv4?
2. If "no" to above, then it would be prudent to *also* set ip6tables rules as well if I want to maintain an active firewall, correct?
3. Does ip6tables rules have the same syntax and behavior (more or less) to iptables rules - i.e. can I just copy my iptables rules & change "iptables" to "ip6tables"?
4. Any gotchas or issues that I should be aware of?
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Oct 16, 2009
I'm behind a modem router with firewall and SElinux enabled by default - but checking my mail this morning I noticed several ' delivery failures ' ( allegedly ) from hotmail referring to mail I hadn't sent. When I checked the spam folder for the on-line side of my mail account there were more failure notices. Two points that may be relevant, one is the recent Hotmail exploit, the other is that this only occurred with the address I use for railway matters, and some people cc to everybody, so it's odds on that address is on a good few computers. On one occassion when I checked my spam folder on-line I found spam which claimed to be from myself, so I know the ' send ' address can be spoofed, is this the explanation, or is it a new kind of attack linked to the Hotmail exploit?
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Aug 30, 2010
I've setup ufw rules on my system but noticed that the rule i created to allow traffic from my local network is still dropping some RST packets.here's part of the output of dmesg
[43627.361500] [UFW BLOCK] IN=wlan0 OUT= MAC=00:16:ea:03:9c:3a:00:1f:a7:3d:d5:eb:08:00 SRC=192.168.0.4 DST=192.168.0.3 LEN=40 TOS=0x00 PREC=0x00 TTL=64 ID=2210 PROTO=TCP SPT=59521 DPT=9000 WINDOW=0 RES=0x00 RST URGP=0
[code]....
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May 8, 2011
I have 3 network interfaces on my Linux Router :
Interface - Gateway - Type
Code:
br0 - 192.168.0.1 - Internet
eth2 - 192.168.1.1 - LAN
tun0 - 10.0.0.2 - VPN (via br0)
What I'd like to do is to route all TCP packets coming from eth2 to tun0 where a VPN client is running on 10.0.0.2. If I delete all default routes and if I add a new route to tun0 like :
Code:
route del default
route add default gw 10.0.0.2
Everything is fine, and everyone on eth2 can reach the Internet using the VPN access. Now the problem is that my VPN client does not allow any other protocols other than TCP. And I also want to allow VPN access only to eth2, no other LAN nor the router itself. use iptables to filter any TCP packets and mark them, so they can be sent to tun0, while any other packets can reach the Internet via br0 (192.168.0.1). I found on the Internet that we can mark packets before they get routed. Using the following commands :
Code:
iptables -t mangle -A PREROUTING -j MARK --set-mark 85 -i eth2 -p tcp --dport 80
ip route add table 300 default via 10.0.0.2 dev tun0
ip rule add fwmark 0x55 table 300
First of all, --dport 80 never work... :/ I wanted to filter TCP 80 packets coming from eth2, but none of them seems to be HTTP packets... oO (very strange...). Nevermind, I decided to forget about the --dport option. I use the "iptables -L -v -t mangle" command to see how many packets are marked, and it is working fine, all TCP packets coming from eth2 are marked. Now the problem is that none of them are routed to tun0 they are all respecting the "route -n" rules... and not the "table 300" rule I have created.
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May 23, 2010
I am trying to write a udev rule for my headset but i don't understand where i get the information to make the rule. I know i need to add
Code: RUN+="bash /home/luke-jennings/headset" at the end of it so the script i wrote runs. I don't know how to get any of the identifying info for the headset and which bits to use where. How do I get the information?
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Apr 19, 2011
I have a trayless SATA hotswap bay that is really terrific for quickly attaching and removing SATA hard drives. I'm trying to write a udev rule to create a symbolic link to the device node for the drive that is attached through the hotswap bay (/dev/bay -> /dev/sdX). This eliminates any ambiguity when performing destructive tasks (fdisk, etc). I'm running squeeze amd64. I've read through several tutorials and have it working somewhat. Here's the output of udevadm info for a drive attached via the hotswap bay.
looking at device '/devices/pci0000:00/0000:00:11.0/host7/target7:0:0/7:0:0:0/block/sdb':
KERNEL=="sdb"
SUBSYSTEM=="block"
DRIVER==""
ATTR{range}=="16"
ATTR{ext_range}=="256"
ATTR{removable}=="0"
ATTR{ro}=="0"
ATTR{size}=="156301488"
ATTR{alignment_offset}=="0"
ATTR{capability}=="52" ....
Here is my udev rule
DEVPATH=="/devices/pci0000:00/0000:00:11.0/host7/*", SUBSYSTEM=="block", SYMLINK+="bay%n"
This produces the desired behavior and gives me an fdisk-able device node. The problem I am having is that the "host" component of the DEVPATH varies from bootup to bootup. I'm just using on onboard SATA, host2-7, specifically host7. There is also onboard PATA, host0-1. It seems to just be random which "host"s are assigned to which controller. For example, the next time I boot the system, the onboard SATA will be host0-5 and the onboard PATA will be host6-7. In this simple case, I could just write 2 rules, one for each possibility and it would still be correct because of the different PCI addresses of the two controllers. But on systems with more SCSI (uh... libata, actually) controllers, a "host" file can point to different physical ports between bootstraps. This would be bad. Does anyone know of a way to write a rule to tie a device node to a specific physical SATA port on the motherboard/hba?
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Jul 19, 2010
Currently I'm looking into implementing mod_security on all our apache servers. The installation on CentOS 5.5 comes directly with the "Core Rule Set" by the mod_security devs (curiously Debian and Ubuntu do not carry these) They also offer the Enhanced Rule Set for mod_security in a commercial package [URL] The main point there in their info link is the first point
Quote:
Tracking Credit Card Usage as required by the Payment Card Industry Data Security Standard However acc. to this wiki article ( http://en.wikipedia.org/wiki/Payment...urity_Standard ) that specific requirement isn't stated anywhere, as well as my colleague who's working on the PCI-DSS compliance for our code/servers/etc. mentioned that he hasn't heard of this specific requirement either. So my question would be if anyone has any experience with their ERS package and if it's needed for the PCI-DSS compliance compared to the requirements given in bullet points @ wiki article.
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Jan 20, 2010
I want to inject a packet with specified TCP options: Maximum Segment Size, Window Scale Option, Timestamp Option... The man page mention very little about that:Quote:-o TCP-options-fileThis will cause nemesis-dns to use the specified TCP-options-file as the options when building the TCP header for the injected packet. TCP options can be up to 40 bytes in length. The TCP options file must be created manually based upon the desired options. TCP options can also be read from stdin by specifying '-o -' instead of a TCP-options-file.I don't understand what TCP options file structure is? ASCII, hex or raw? One way to try: in Wireshark, select the Follow TCP stream option of a packet, save as with some types: ASCII, hex... and use it for input:
Code:
sudo nemesis tcp -v -fS -D localhost -o /path/to/<TCP_options_file>
the output displays:
[code]....
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Jan 14, 2010
I am new to Ubuntu almost installed it after windows showed blue screen 4 ever n ever. However after installing ubuntu whenever I log in windows it doesnt detect any network connection but when I use Ubuntu it automatically does can it be that Ubuntu is causing any problem? And how to check how many packets are being sent and received through my wired network and do I have to install any drivers for my modem in Ubuntu.
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Nov 21, 2010
I am trying dump some packets using tcpdump and it does not seem to be working.
System is fedora12
TCPDUMP v4.1
Libpcap v1.0
I even rolled my own,
TCPDUMP v4.1.1
libpcap v1.1.1
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Feb 7, 2011
I'm sniffing network packets in ubuntu, I need to write these packets as raw bytes to memory but libpcap give packets in its special format. how can i save and recover packets in byte format?
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Dec 20, 2010
I guess this is the right place to put questions about iptables, so forgive me if it is not.I have a MySQL database which I need to allow connections to: 1 - the internal network; 2 - the web server (Apache) connections;3 - A user who is out of this network in a range of dynamic IP.Let's suppose the range IP for this user is 179.4.247.0-179.4.247.254 and the server; where is MySQl and Apache is 60.22.30.232. This user will use the windows client MySQL tool to make connections into this database.
So I think these rule below allow connections to the internal network and apache:
iptables -A INPUT -i eth0 -m state state ESTABLISHED,RELATED -j ACCEPT
iptables -A INPUT -i eth1 -m state state ESTABLISHED,RELATED -j ACCEPT
[code]....
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Sep 1, 2011
I need help creating an iptable rule. The iptables are installed on my router. My router also connects to a "hide my a**" vpn account
at 79.142.65.5:443 The goal is to somehow force the traffic to go through the vpn, because what sometimes happens is, the vpn connection drops (for what ever reason) and my real ip becomes exposed. Basically, I want to block "myself" from accessing the Internet when not connected to the vpn because of privacy concerns.
Below is my iptables. It has the 3 default chains and it also has many custom user chains. I need to know what kind of a rule to add, What interface to apply it to (lo,tun0,br-lan,eth1) and the correct chain to insert into.For example, you could tell me something like:
Quote:
FORWARD chain, change rule 1 to
iptables -R FORWARD 1 -j zone_wan_MSSFIX -p tcp --destination-port 443 -i eth1
Obviously, That was just a guess, I need someone that knows iptables to help me.
Code:
Chain INPUT (Policy: ACCEPT)
Rule # Traffic Target Prot In Out Source Destination Options
Rule 1 72.95 KB DROP all * * 0.0.0.0/0 0.0.0.0/0 state INVALID
Rule 2 1.11 GB ACCEPT all * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED
[code].....
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Nov 17, 2010
I'am using the explicit match 'quota' with iptables. I wonder how can I save quota between restart for every rule. All the quota resets at reboot.
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Mar 4, 2011
I am using squid on my fedora box as a proxy server.By default the iptables (Firewall) service is on.To allow web pages to my client machines i stop the iptable service.
#service iptables stop
By doing it client computers start browsing.kindly how can I add a rule so that without stoping firewall client compter work fine.my perver IP address is 10.1.80.10
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Feb 23, 2010
I'm not an iptables expert. Anybody know how to create a rule/chain that will log info similar to what tcpdump -s0 would do?
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May 16, 2011
How do I redirect all the UDP traffic on port 27016 of my current dedicated server to a new IP port 27015 using IP tables?
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Apr 30, 2011
i dont know why packets dropped? and something else what are those numbers for default policy in [] means?this is rules:
Code:
# Generated by iptables-save v1.4.4 on Sun May 1 00:09:57 2011
*mangle
[code]....
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Sep 1, 2010
I setup a SSH server on my computer on a very high port, so that my brother could surf the web through my computer from Iran, since the majority of websites are filtered there.
Today, he told me he cannot connect to my computer. That's why, I got suspicious that they are doing packet based filtering instead of port. Then I decided to change the port to 433 for https, but one of my friend told me that they just banned https in Iran as well.
I was wondering if there's any way I can manipulate SSH packets between two computers so that my brother's ISP won't figure out he's exchanging SSH packets?
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Dec 17, 2010
My machine is trying to communicate with another computer. I�ve blocked the traffic with this machine with iptables (input and output traffic), but I want to find the origin of this traffic. There�re 90% of probabilities it�s a trojan, and I want to find it.I have logged the packets with iptables (and then dropped), but with this I don�t know the proccess source.I�ve tried with netstat -o, but I don�t get nothing.How can I see the Process source (i.e. the PID) of this traffic?The traffic are TCP packets, with SYN flagged active (my machine is trying to establish a connection with that IP).
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Jun 8, 2011
My VPS host a mail, blog and web site. So i want to block port i not use. The port that i use is 80,21,2022,443. The other port will be drop. I want to block bad packet and all packet that not related. Can anyone how to write in iptables?
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Oct 18, 2010
I am trying to figure out what command to use to show the number of DROPPED and INVALID packets that the firewall is handling.I'm going to put these commands into a log analyzer script which will run every 15 minutes with cron. The firewall is running and operating the way I want it to. I'm running CentOS 5.4.
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Apr 6, 2011
i have configured racoon (ipsec tunnel) between 2 hosts and i am afraid of unencrypted ICMP which appears in TCPDUMP logs. There ale also encrypted ESP packets. Is this result of wrong racoon configuration?
172.16.220.133
Code:
[root@localhost ~]# cat /etc/racoon/racoon.conf
# racoon.conf
path pre_shared_key "/etc/racoon/psk.txt" ;
remote anonymous
[Code]...
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Nov 26, 2010
The iptables has every rule set correctly, the users in the subnet works great, but I have the following issue.every user connect to a mysql running on the internet through the port 3306, the forward and masquerade do the job. Now I have a user in the outside, and he wants to connect to a mysql in a certain machine (Not the gateway), prerouting rules solve my problems, but all the packages from the inside users goes now to that certain machine. I would like something like if the package passed trough masquerade don't pass trough the prerouting rule, and if it come from the outside (Not a package that come from a petition from the inside) pass trough the prerouting rule.
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