We are currently experiencing an SYN Flood attack on our primary production server and are looking for some help in resolving the issue.
Running:
Novell SUSE Linux Enterprise Server 10.2-64
SuperMicro X7DBR-E Intel Xeon QuadCore DualProc SATA [2Proc]
Processor Intel Xeon-Clovertown 5320L-QuadCore [1.86GHz]
8GB Memory
@ Softlayer DC in Texas.
Need help within the next hour or two. Please ask any necessary follow up questions and how you might go about resolving the issue (i.e. SYN Cookies, etc.)
It's literally thousands of those requests overloading apache. The server is fine, the load average is like .8. But none of the website are loading.
We're hosting with ThePlanet, and they're doing a great job at blocking a huge portion of the attack. But we're still getting hit pretty hard. I've got APF installed, and 3 or 4 anti-dos scripts.
Every once in a while a page will load for the websites, I think we've got just under 50 legit connections.
installed apf but it slowed down the server to a crawl which made my clients really unhappy so had to remove it.
The bandwidth is constantly staying at 30Mbps with slight bumps here and there but every day around 7pm it drops completely to normal levels and the flood stops. It starts back up around 7 in the morning.
How can I best work with a syn flood? I've tried the apf, deflate-ddos etc.... and don't work. Even tried litespeed etc but doesn't work against a 90mbps attack.
If I get a few servers, how would I have it setup to best defend?
We got hit with a huge bandwidth bill for last month. It was 4X our usual bill. The ISP said that we were the victim of UDP flood attacks from an outside server. We have a sonicwall router and the firewall seems to be blocking the port that the ISP claims the attacks can from. Is it possible that the attacks would still count towards our bandwidth usage even if the connection is refused by our firewall? Our ISP uses 95th percentile billing.
One of the servers have 1 account on, but seems like its extremely attacked. I cannot SSH and many packet loss. so I asked softlayer and they access it and said its a SYN Flood as from the /var/log/messages (I cannot see it as the server is not accessable) they put the main public ip under Cisco guard but still didn't help. when I asked for any solution, unfortunaly I were told there isn't and have to wait the attackers to stop as it comes from MANY addresses that iptables even won't help.
Isn't there any solution (software-hardware) to stop that ?
one of my costumers server is getting ddos attacks. I solved syn and get attacks with litespeed web server but I have another problem. They started to do udp flood. I m losing connection to my server. I bought new server with 1 gbit port for solving it.
all day i receved msgs of BFD someone trying acess server, how to stop it, exemple: Executed ban command:
/etc/apf/apf -d 221.186.164.233 {bfd.pure-ftpd} The following are event logs from 221.186.164.233 on service pure-ftpd (all time stamps are GMT -0500):
Oct 25 13:52:37 svr1 pure-ftpd: (?@221.186.164.233) [INFO] New connection from 221.186.164.233 Oct 25 13:52:37 svr1 pure-ftpd: (?@221.186.164.233) [INFO] New connection from 221.186.164.233 Oct 25 13:52:38 svr1 pure-ftpd: (?@221.186.164.233) [WARNING] Authentication failed for user [router] ....
I use Outpost Firewall to view active connections to my server. If I don't restart the httpd service on a regular basis my server will grind to a halt from being flooded by robots.
I currently have the service set up to restart at Midnight and Noon every day. Sometimes that's enough, lately it's not. For example, I checked an hour ago and I had 385 connections to httpd. At least 50% of the connections were robots - tons of the same IP addresses and they're just crawling the site.
Almost all of the connections show up as less than 1kb bytes received and 0 bytes sent per connection.
I already have a good 20 connections by these robots and the connection time shows as 11 minutes... I just browsed to a web gallery page on my site figuring that'd be mildly "intensive" on connections with all the thumbnails and my connections aren't lasting more than one minute.
So, what's with all these connections that are lasting 10+ minutes? I've even got one connection that has an Uptime of 30 minutes, bytes sent 65811, bytes received 180. It seems like something with these robots doesn't terminate correctly...
what to do so these connections quit jamming my server up? It's like a very very slow DOS...
I serve large professional documents, and sometimes links to them end up on social media. No big deal, but I think people clicking on them from tose social media sites don't have a clue. They think they're being directed to small page, when in fact they are downloading megabytes of pdf -- myfile.pdf. So what I've started to do is to redirect requests from social media to an archive page, where they can see specifically what document they are trying to get, and recognize its size before they ask for it. No problem, right? I just do
I'm sure that i have Trojans and Viruses on my Server but every time i contacted My Company they ask me to pay money and then they will check and scan my server
so is it any Free application which can scan and remove all bad files on my Server? i'm looking for free applications to scan the whole server
My server stop responding, I couldn't access via webmin or ssh, and DNS were not responding, so I have to ask for a reboot and now everything is fine.
Looking at the logs I found this:
Code: Jul 18 19:23:12 server sshd[18484]: Failed password for root from 61.145.196.117 port 56817 ssh2 Jul 18 19:23:12 server sshd[18485]: Failed password for root from 61.145.196.117 port 60227 ssh2 Jul 18 19:23:13 server sshd[18488]: Failed password for root from 61.145.196.117 port 38038 ssh2 Jul 18 19:23:15 server sshd[18493]: Failed password for root from 61.145.196.117 port 49884 ssh2 Jul 18 19:24:30 server sshd[18497]: Failed password for root from 61.145.196.117 port 37929 ssh2 Jul 18 19:25:06 server sshd[18521]: Did not receive identification string from 61.145.196.117 Jul 18 19:25:09 server sshd[18508]: Did not receive identification string from 61.145.196.117 Jul 18 19:25:14 server sshd[18505]: fatal: Timeout before authentication for UNKNOWN Jul 18 19:26:00 server sshd[18509]: Did not receive identification string from 61.145.196.117 And searching that IP on google I found it here: http://www.tcc.edu.tw/netbase/net/in...?fun=240&prd=3
And is flagged as a SSH Attack.
Any ideas why my server stopped working? and how to prevent it?
My site currently in prolong HTTP flood attack since 2 weeks ago. The attack was never stop and for this moment i could only mitigate the attack using my own firewall (hardware).
Since my ISP is not interested to help from upstream, even provide any mitigation services, i could only doing mitigation on my own source or using proxy services alternatively as well, but i've chose to tried on my own. I've tried once on one of well-known mitigation services out there but it seems not fully satisfied me since most of legitimate traffic is blocked from their source.
What i could do now is keep staying alive as well as will not going down on whatever situation becomes worst (but if the attack change to udp attack, i couldn't help myself coz there must be high incoming bandwidth into my network). My network is totaling 10MB last time but since this attack i've been forced to subscribe for 30MB in order to keep balance on the attack.
I've blocked all access except for my country and some other neighbours. If i change policy to allow all countries, the load of firewall will become max and after that hang will hang in less than a minute. I've done load balancing of 4 servers (8GB memory each one) and it seems the condition is getting under control with slight problem of server hang (memory shortage) and very limited keep alive connection.
Now what am i thinking is to buy a router objectively to null route incoming specific IP of countries so i can change my firewall policy to allow all connections as well as to help the firewall itself release its burden halting blocked IP that currently keep hitting itself that could might impact its performance.
Which brands of router is possible doing this thing?
Do you have some other suggestions instead of buying router?
i am just having one issue in one of my highly visited website hangibar.com, its being hosted in softlayer, we are facing synattack too much in this website.
the solution which microsoft given in their website related with tcp/ip registry entry but thing is same , some where and some connections become increases too much over tcp/ip. due to that reason website become very sticky and it stop functioning the execution of sql process, during this issue i have to restart the server to establish a fresh connection.
When i tried to view this http://gihkus.com/Lnx.txt it seems to be attack on my server. http://gihkus.com/Lnx.txt is not hosted by us. I have disabled perl support on all domains hosted on our server but still we are under attack. There is nothing special in /tmp.
Over the past day one of my servers has seen a huge rise in incomming traffic (from normal web requests to a constant 4Mbit/s, peaking upto 80Mbit/s). My outgoing traffic has remained at its normal profile, so I am pretty sure that these are not web requests, and it does not seem to be having an adverse effect on the server (the site still runs perfectly well and quick and load is still less than 1).
However, I am unsure as to how to identify what this traffic is? Are there any easy ways to tell on a FreeBSD server what the source and type of incomming traffic is? I have tried playing with netstat, but an not getting anything useful - I would like to see which ports are involved.
Am Really suffering here for ddos attack ( apache - pop3 ) every week my server under attack am using APF but now am really wanna get red from it am looking for a powerfull firewall I do not know if CSF Could stop this attack like limiting receiving SYN from an ip or any other policy another thing . i have get this rules from forums but am really weak at iptables rules so can any one help my if these rules useful or not . against Dos attack:
iptables -t nat -N syn-flood iptables -t nat -A syn-flood -m limit --limit 12/s --limit-burst 24 -j RETURN iptables -t nat -A syn-flood -j DROP iptables -t nat -A PREROUTING -i eth0 -d (dest ip) -p tcp --syn -j syn-flood
