Banning the IP is the best way to protect your server but of course, attacker can use another IP and use a lot of your bandwidth until you find and ban the IP. So the only thing we can do to prevent this is, block the packets my iptables length module.
I check the bandwidth usage through "iftop". Incoming traffic is always like 120kb/second and that has to be that way because the traffic enters my server no doubt that it gets dropped by iptables later.
The actual thing what the Ddos ( UDP Flood ) does it that it causes an outbound traffic that eats up like 5mb/second easily and my servers lag. Only if the IP is banned, the outbound traffic comes to an end.
Now I want to use the length module to block it but it just won't work. I've tried the following and shuffled them too but no help.
Code:
iptables -I INPUT -p udp -m length --length 15 -j DROP
iptables -A INPUT -p udp -m length --length 15 -j DROP
Packet length is 15 according to tcpdump:
Code:
19:49:34.504864 IP fms-02.colt.net.belgamanagement.be.56413 > nyc.v1servers.com.20100: UDP, length 15
I have a fresh installation of CentOS 5 I'm using for a server, and I'm having issues with port configuration. I have iptables running, and it started with no /etc/sysconfig/iptables file. I added a few basic rules (port 53, port 10000 for webmin), saved the file, and restarted the service. I tried connecting to webmin, scanned ports, and traffic was blocked. I set iptables to allow all traffic and restarted the service, and it still showed basically every port as being blocked. It seems port 80 and port 22 work for some reason, even when I tell iptables to block all ports.
I'm not sure what's going on here. Iptables is reading the /etc/sysconfig/iptables file, and if I use lynx localhost:someport it responds as it should according to the file. However, if I try connecting by IP, it's like there's some other firewall or something running that does whatever it's configured to do.....
specs: toshiba lappy 110gb hdd, 1gb ram, core 2 duo 1.6ghz, nvidia 7600 windows xp pro service pack 3 jaunty jackalope
my problem is: i wanted to repartition (shrink xp and create partition for data storage) my hdd using gparted live cd 0.5.2-9. everything went fine until i clicked exit and reboot. after the cd tray automatically ejected i got a flood of "VFS: busy inodes on changed media or resized disk srO". this doesnt stop until i press enter. after that it reboots normally and there is no problem with the os.
my questions: 1) is that flood anything bad, is there a way to avoid this. i read somewhere that the problem is solved when using the terminal sudo eject - then push back the cd tray - then sudo eject -t. i tried that but it said failed because gparted cd is in use.
2) the first time that happened i didnt know what to do, so it flooded like for 15min or more until i pressed enter. my question is if the flood is being saved anywhere on the pc so that i have to delete it?
and a question regarding extended partition: 3) i have 50gb left that i want to use for data storage. i read that you can only have one extended partition. so since there is already one extended partition from ubuntu, i cant have another one for windows? so i can only make the data partition as primary or is there another reason why the "create extended partition" is greyed out?
last question: 4) when i set up the partition for swap i made it 1032gb big but in gparted it shows 980.53mb. is that still enough or why is it like that because somehow the sizes of the partitions seem a bit different than how they originally should be. im actually used in seeing the size shrinking a bit but i found it weird that the ubuntu partition shows 4.76 when it should be 4.5gb. i know its not much different but im just curious to know why..
partitions order: windows - unallocated (-->data partition) - ubuntu (primary) - home folder (extended) - swap
in windows the partitions are shown as: windows xp (31,74gb) - unallocated (50,05gb) - 4,76gb unkown - 24,27gb unkown - 981mb uknown
in gparted: its almost the same, only difference: there is unallocated space (7 or 8mb) between home folder and swap
my computer froze solid, and it would not react to anything. X didn't react to Ctrl+Alt+Backspace, not Ctrl+Alt+Del, so I had to turn it off using the power button.
This is the first time my computer freezes like this, the log files did not reveal any HW errors. Is it possible that someone in the channel did not like my level of Java skill, and flooded me to disconnect?
By the way; Im using slackware 13.1 with the default kernel (2.6.33.4) and irssi as IRC client.
I know that if you eg. ICMP-flood someone, the traffic will be denied and, but can it provoke other behavior from the computer?
So my question is; can a IRC flood/DDoS attack cause a computer to freeze sub zero?
I follow this instructions but after iptables-restore < /etc/iptables.test.rules I see this error # iptables-restore < /etc/iptables.test.rules Bad argument `#' Error occurred at line: 3 Try `iptables-restore -h' or 'iptables-restore --help' for more information. The line 3 is the same as the link - # Allows all loopback (lo0) traffic and drop all traffic to 127/8 that doesn't use lo0
i have a question regarding iptables.i have a server running ubuntu server 10.04 with 2 nic's, i want to use it to filter the internet trafic of the people in my network ussing dansguardian and squid. they both work fine.the only problem is how to get iptables to deal with this the right way.
Trying to install 10.10 netbook edition on my MSI U230 netbook from a USB drive. Keep getting the error "hyper transport sync flood error occurred on last boot" Press F1 to Resume. F1 causes just a reboot and the same thing happens. Anyone seen this error? It happens with both the netbook and desktop version.
I run a Centos server that quite a few people have access to. I trust every user on the system, but i've had problems before like one user's account gets hacked and someone starts using my box to DDOS. Each user has their own ip.. And I would like to write a script or use an existing solution (if one exists) to monitor number of tcp/udp connections each minute and see if it's unusually high. I don't want it to stop the flooding or anything, I just want to be notified by email or something.
I've been trying to forward some ports using iptables for some time now, but still haven't figured out how to get it to work..What i'm trying to accomplish is to forward all traffic from port 80 to port 8080, and all traffic from port 443 to port 8443, this because i would like to run tomcat as a non-root user, and the original ports can only be used as root.. I've currently setup my iptables like this:
# Generated by iptables-save v1.4.2 on Wed Nov 10 16:44:45 2010 *nat :PREROUTING ACCEPT [39350:6120333]
Rather new to Ubuntu. I was wondering for advice on a basic iptables configuration blocking all incoming/forward and just allowing outgoing to http(s) and dns of course.
eth0 is configured through a dhcp server connected directly to it. [URL]...the answer of the server is a UDP to 255.255.255.255. Please tell me how can it pass through this iptables configuration, because it does.
Code: iptables -nvL INPUT (policy DROP) 3281 201K ACCEPT all -- eth1 * 192.168.69.0/24 0.0.0.0/0 0 0 ACCEPT all -- lo * 127.0.0.1 0.0.0.0/0 0 0 ACCEPT all -- lo * 192.168.69.1 0.0.0.0/0 0 0 ACCEPT all -- lo * 93.114.xx.xx 0.0.0.0/0
I am trying to set up a DMZ host - that is, one multifunctional PC between the WAN and the LAN. I've started with a basic router, and expanding upon that as the need arises. I am currently trying to gain access (from the WAN) to a website hosted on one of the servers in the LAN, but I am having trouble accessing the host from the WAN; I think my iptables configuration may be too restrictive. On the DMZ host, I'm using Debian (Etch). I have setup dhcp3-server, a script to configure iptables and pound (reverse-proxy). The (virtual) machine has 4 network cards: eth0, eth1, eth2, eth3; eth0 is the WAN, eth1 through eth3 serve 3 different virtual LANs.
All machines in the LAN (except one windows 2008 server - I might want to address that problem later) get their IP adresses correctly via dhcp from the DMZ host. All machines on the LAN can access the internet (including the 2008 server if I configure it manually) as they should. If I access http://localhost on the DMZ host, pound reports "The service is not available. Please try again later." - as it should.
I can ping the DMZ host from the WAN on 10.0.0.79 However, if I try to access the DMZ host from the WAN (http://10.0.0.79) I get "Unable to connect" from firefox. I'm sure this is not a pound problem, so I think it's in the iptables, or maybe I should be installing some extra software that I'm unaware of.
one thing I'm not quite certain about is suitable limit rates for SYN, LOG & ping flood prevention. I suppose it depends a bit on traffic, as well as bandwidth. However, I don't want to limit the former. FWIW, I expect about as much traffic as a country road in the middle of nowhere, and my bandwidth for requests is 15 Mbps (Don't laugh. Content delivery is a pathetic 2 Mbps. That's a residential cable connection for ya...)Of all the tutorials/examples, I chose to go with Rusty Russel's limits, though they're dated 2002. Thus an excerpt of my firewall "script":
I'm having some trouble with the configuration of the iptables. I want to setup a network server to serve as Fail Over (for my 2 ISPs), DHCP and DNS. I have 3 network cards, 2 connected to ISP's routers and 1 that serves as UPLINK for my switch.
I want to add some Iptables rules so I can achieve what I want to do. The problem is that the rules I try to use, they have to effect.... they don't load, here are the rules I am trying to add:
In December 2009 I switched my web-hosting package with 1and1 to their best VPS package. What a difference! At this time I knew absolutely NOTHING about Linux sys admin stuff. Now, I know a little more I now run 'several' VPS instances (all with 1and1). Back to the problem then... On all my boxes I run CentOS 5.5 (Linux 2.6.18-028stab070.4) with various different versions of Plesk (9.5.2 and 10.2.0) The VPS instances themselves are on Virtuozzo nodes. As you may know, Virtuozzo has a firewall GUI allowing modification of iptables. I only use this when I make a mistake and cannot SSH. My 'original' iptables: (the VZ chains are controlled by the Virtuozzo container)
if this iptables chain limits the number of connections to 3 per second and 100 per second respectively, is this still secure or is there no point in having this rule? If the rule is a good one to have, then how can I allow http connections to bypass this chain/rule?
I managed to set up an openvpn server, ip-forwarding and a nat iptable rule for that.
Almost everything works as expected, but my problem is:
Smartphone -> VPN -> Internet ==> works (by ip and hostname) Smartphone -> VPN -> machine in my local network by IP ==> works Smartphone -> VPN -> machine in my local network by its hostname => DOES NOT WORK Machine w/ VPN server -> ping to machine in local network by ip or hostname => works
So, i wonder why i cant access a local machine through the vpn by its hostname. I guess I'm missing a forwarding rule??
iptables dump: # Generated by iptables-save v1.4.21 on Sun Feb 7 20:56:52 2016 *nat :PREROUTING ACCEPT [786:59064] :INPUT ACCEPT [728:53047] :OUTPUT ACCEPT [19:1487] :POSTROUTING ACCEPT [20:1576] -A POSTROUTING -s 10.8.0.0/24 -j MASQUERADE COMMIT # Completed on Sun Feb 7 20:56:52 2016
I'm intending to replace my current router (486DX2 w/16MB running FREESCO which has been faithfully working 24/7 for well over a decade) with a debian box with a bit more grunt and newer features. I'm currently setting up my iptables ruleset and am after a bit of advice re the FORWARD policy. A few example rulesets I have found set the default policy to DROP and the have two lines for each port forward, one to allow the traffic and one to direct the incoming packets to the correct machine.
I'm thinking of setting the default policy to ACCEPT to cut down on typing as my default INPUT policy is DROP and unless there is a valid FORWARD rule for a particular port, the packets aren't going anywhere anyway. Or have I misunderstood something. My googling returned heaps of example scripts & not much intelligent commentary. Alternatively, what do you all use to configure & maintain your debian gateways; hand rolled iptables rules, or any toolset recommendations?
After resetting a pc running lenny I get iptables errors at boot ("resource temporarily unavailable", "bad rule" etc). "setting up firewall" (Guarddog) is not followed by any errors and the firewall apparently operates ok.How can I restore my iptables to the default installation values?
I have a strange iptables issues. I have just built a new Debian install and starting adding some real basic rules (see below) the problem seems to be that the localhost itself can't get any returning traffic. That is, it seems to be allowed outgoing traffic but not the connected, returning traffic. Ordinarily allowing Established Connections would resolve this, see the rule below, but it hasn't. Why this doesn't work. Removing the last DROP in the INPUT chains obviously makes the traffic work!
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT iptables -A INPUT -j ACCEPT -p tcp --dport 22 iptables -A INPUT -j ACCEPT -s x.x.x.x iptables -A INPUT -j ACCEPT -s x.x.x.x iptables -A INPUT -j ACCEPT -s x.x.x.x -p tcp --dport 80 iptables -A INPUT -j ACCEPT -s x.x.x.x -p tcp --dport 8080 iptables -I INPUT 1 -i lo -j ACCEPT iptables -A INPUT -j DROP
I'm trying to use these cookie cutter rules that I found. But every time I use them, after a few seconds my wifi connection goes dead. The exception was the first time I used then. Which lasted me a couple of minutes.
By dead I mean I can no longer open a webpage or ping google.
iptables -N LOGGING iptables -A INPUT -j LOGGING iptables -A OUTPUT -j LOGGING iptables -A LOGGING -m limit --limit 2/min -j LOG --log-prefix "IPTables-Dropped: " --log-level 4 iptables -A LOGGING -j DROP
I have a server that I can only access via SSH (it's located far away) and I would like to secure it by blocking all ports except the ones that I need (which are HTTP and SSH). I still want to be able to make outgoing connections to enable software updates and other things.This is my iptables -L -n :
Code: Chain INPUT (policy ACCEPT) target prot opt source destination ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED DROP tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpts:1:21 DROP tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpts:23:79 DROP tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpts:81:65535 code....
In my opinion, this should block all incoming packets except the ones on port 80 and 22, but allow responses to outgoing connections. But a wget http://google.com does not work, it can't establish the connection.
Maybe this is not the best style for iptables rules, but I want to be absolutely sure to not accidently lock myself out from SSH, so I chose not to configure a "block-everything rule".
Does this configuration not enable incoming packets from connections initiated from inside?
I have installed a linux server in my office to run 16 machines. Its main use will be a internal mail server but will be also running websites.
I have installed Ubuntu 9.10 server x64 and have got apache running.
I am looking for the simplest more robust solution for smtp, pop3 and imap. I have only ever used qmail before and found it a pain to configure and its getting old so I though I should probably try something new. I have not much experience with running pop3 or imap on linux so would love a suggestion on that.
