Most Ruthless Dictionary Spam Attack
Sep 14, 2007
RHEL3/Cpanel/Exim
So one of my domains is getting a dictionary attack. It is a popular domain and "big deal" it happens all the time. Well, this time it is the most ruthless distributed dictionary attack I have ever seen.
Today marks the one week period and emails are flooding in 10 to 15 a second (of course none of them ever get delivered). It is like hail pounding on a thin tin roof and the denial/logging alone has the server load at least quadrupled!
Oh yeh, the best part. I have a beautiful list of over 7,000 banned IP addresses (and growing every minute, now THATS DISTRIBUTED!).
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Feb 19, 2007
My site is being attacked by what appears to be a dictionary attack on my mail account. They are sending e-mails to random accounts at my domain from random e-mail accounts from somewhere else. Each of their messages is coming from a unique e-mail address and a unique IP address.
Now, we have some dictionary ACL installed that basically blocks any IP address that is caught doing this. So we are blocking tons of IP addresses, but they keep coming at us with new ones. We also have it setup so that the mail is rejected right away for any accounts that aren’t actual e-mail accounts of yours. However, they are hitting the server so hard that it doesn’t seem to be making any difference.
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May 16, 2007
We've been seeing sluggish performance on our mail gateways, and so I started doing some digging in the logs. It looks like we are filling up with messages like:
2007-05-16 12:22:16 Connection from [xx.xx.xx.xx] refused: too many connections
We have our max connections set to 20 (total, not host-specific) in exim4. So I started tailing the logs, and sure enough, we are getting bombarded with requests to randomstring@ourdomain.com coming from all over the map. The requests are getting denied of course, but that doesn't help the connection issue since they are consuming all of them, preventing real mail (for the most part) from getting through.
What is the proper way to deal with something like this? I could certainly just up the max connections value from 20 to 40 or 50 or whatever, but I'm not sure what kind of performance impact that will have on the rest of the traffic going through our gateways.
Since the spam attempts are coming from all over the place, it doesn't seem like I can just firewall out a few addresses and be done with it.
This particular rack is a cluster of web and database servers behind two gateway boxes, which handle the mail traffic (so this problem is on the gateways, the actual mail server itself sits behind the gateways and never actually sees these fake emails).
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May 28, 2014
I'm getting a big problem on my server.
From 1 week until now I got 4 spam attacks. The attacker is the same, because the emails sent are iqual.
The technique is also the same, they use an email account (compromissed password) and send emails through smtp server.
When I detect the attack, i do:
1. identify the compromised account
2. Change password from the compromised account
3. Stop qmail
4. Clear queue with qmail-remove
5. Start qmail
The problem is that they already used 4 diferent domains since the first attack. So, here is my problem, how do they discover the passwords?! How can I solve this problem? I have hundreds of emails accounts and can't change it all.
CentOS release 5.10 (Final)
Plesk 11.0.9Â
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May 22, 2014
I need reinstall qmail after spam atack and follows the post.URL....It says:
rpm -Uvh --force psa-qmail
but my system return an error message..error: opening psa-qmail failed: it does not existe file or directory (error: la apertura de psa-qmail falló: No existe el fichero o el directorio)
rpm -q psa-qmail
return
psa-qmail-1.03-cos5.build1013120126.11
And my system is CentOS
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Nov 24, 2007
I have to deal with a lot of dictionary attacks. One evening, I got fed up with them and decided to do something about it. So, I wrote a service in VB.NET that monitors the Windows event log. I check for too many incorrect login attempts to MS SQL.
If I find someone attempting to dictionary attack, Windows shows the IP address of the invalid login attempt in the event log. So, I parse the event message, grab the IP address, and use IPSec to block the would-be intruder. Excellent!
Ok. That takes care of SQL attackers. But, what about RDC (Remote Desktops or Terminal Services) attackers? I started using 2x's SecureRDP. It works great, but the logging feature is broken. It doesn't accurately log the attackers' IP addresses. So, how can I get the IP address of those attempting to login via RDC? Anyone know? There has to be a way.
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Nov 3, 2009
I'm running a dedicated server with CentOS 5
Today I open my email logs and I was surprise by what I found!
Logs like this:
Nov 3 17:23:55 warhead vpopmail[5979]: vchkpw-smtp: vpopmail user not found sys@:118.167.19.58
Nov 3 17:23:58 warhead vpopmail[6010]: vchkpw-smtp: vpopmail user not found sys@:118.167.19.58 ...
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Oct 17, 2013
Microsoft Windows Server 2008 R2 Service Pack 1
Panel version 11.0.9 Update #59, last updated at Oct 3, 2013 02:06 AM
MailEnable version 5
I see in the plesk documentation that the screen to enable SPAM filtering for an individual there is an option to "Move spam to the Spam folder". I don't see that option so I am wondering if it is only available on some versions of Plesk, or in combination with certain mail servers. How to make that option available?
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Mar 11, 2008
Quote:
Mar 10 20:17:55 host kernel: printk: 102 messages suppressed.
Mar 10 20:17:56 host kernel: printk: 3 messages suppressed.
Mar 10 20:18:01 host kernel: printk: 98 messages suppressed.
Mar 10 20:18:35 host kernel: printk: 34 messages suppressed.
Mar 10 20:18:51 host kernel: printk: 189 messages suppressed.
Mar 10 20:18:56 host kernel: printk: 195 messages suppressed.
Mar 10 20:19:02 host kernel: printk: 249 messages suppressed.
Mar 10 20:19:06 host kernel: printk: 36 messages suppressed.
Mar 10 20:19:21 host kernel: printk: 3 messages suppressed.
Mar 10 20:19:26 host kernel: printk: 342 messages suppressed.
Mar 10 20:19:31 host kernel: printk: 509 messages suppressed.
Mar 10 20:19:47 host kernel: printk: 54 messages suppressed.
Mar 10 20:19:51 host kernel: printk: 421 messages suppressed.
Mar 10 20:19:56 host kernel: printk: 542 messages suppressed.
Mar 10 20:20:01 host kernel: printk: 785 messages suppressed.
Mar 10 20:20:16 host kernel: printk: 340 messages suppressed.
Mar 10 20:20:21 host kernel: printk: 337 messages suppressed.
Mar 10 20:20:26 host kernel: printk: 430 messages suppressed.
Or is this something else? It's been going on for about 40 minutes. I seen my load jump to 20, to 100 and back and fourth
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May 24, 2009
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
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Jul 18, 2009
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?
Im using CentOS 5.0
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Jun 11, 2009
i found my site load slowly, the cpu load is good. I run this command
[root@host ~]# netstat -nap |grep SYN |wc -l
526
It's seem my server is having problem with SYN attack. Is there anyway to protect it ?
I'm running apache 2.
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May 12, 2009
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?
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Apr 12, 2008
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.
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Dec 9, 2008
im getting a syn attack and my vps getting overloaded what im doing is banning ip's that gets most connections
after banning server get normal but if there anyway to stop this post method
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Oct 30, 2008
My server is under dos attack (http) , I have installed APF firewall and ddos deflate. I configure them to work together.
now if any IP with more than 100 connections is black listed by dos deflate, I can see it in apf's deny_hosts.rules file.
everything seems correct, but my server still very slow.
the ip which is causing that has more than 1000 request and is blacklisted.
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May 15, 2007
There are lot of perl process with 100% usage on server. When i tried to view error_log it shows following:
[root@local ~]# tail -f /var/log/httpd/error_log
=> `Lnx.txt'
Resolving gihkus.com... 208.98.48.116
Connecting to gihkus.com|208.98.48.116|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 16,577 (16K) [text/plain]
0K .......... ...... 100% 316.78 KB/s
05:26:03 (316.78 KB/s) - `Lnx.txt' saved [16577/16577]
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.
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Jan 4, 2007
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.
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Jul 15, 2007
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
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May 29, 2009
My server is using too many httpd process..I think iam under DDOs attack..I executed the following command..
netstat -an | grep :80 | sort
and the result is this
tcp 0 1491 ::ffff:95.211.10.169:80 ::ffff:213.215.100.110:2263 LAST_ACK
tcp 0 1493 ::ffff:95.211.10.169:80 ::ffff:85.207.126.231:52694 LAST_ACK
tcp ....
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Aug 4, 2009
I have a windows server, and today it has a large inbound traffic, so I tried to disable all web service, and after that, the result of netstat -an shows no connection at all, but the server still has large inbound traffic,
Do you have any idea about this?
What should I do now?
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Mar 19, 2008
Our server is in attack since 4 days. Http port busy all the time.
When I type :
netstat -na | grep ":80" | awk '{print $5}' | cut -d. -f1-4 | cut -d: -f1 | sort -n| uniq -c | sort -n | tail -5
It shows :
[root@ ~]# netstat -na | grep ":80" | awk '{print $5}' | cut -d. -f1-4 | cut
-d: -f1 | sort -n| uniq -c | sort -n | tail -5
2 65.19.130.24
2 83.149.120.9
4 204.15.73.243
35 222.254.103.142
5128
[root@ ~]#
I wonder the hidden IP of 5128 ??? How to know it?
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Jun 21, 2007
The server getting slow with high I/O diskwait then normal, although load is not high.
here is the output of: netstat -anp |grep 'tcp|udp' | awk '{print $5}' | cut -d: -f1 | sort | uniq -c | sort -n .................
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Apr 12, 2009
i had installed anti ddos or firewall,but those are useless.His attacks are such great that The server and all the vps are down now. One told me that I should check the ips and receive ips. The attacker is so skillful .describe the best method to defeat him. Be sides the attacker use diffirenet ips in each attack,I block him by iptables but no use…. His attack occupy all the ram and I have to resetart the server… Now this time his attack lead to shutting all the vps down
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Jan 6, 2009
My website is under ddos attack from some competitors. I don't know yet how big is the attack. The ips of the ddos attack come from all the world.
I have contacted a few hosting companies specialised in ddos proof hosting, unfortunatly the price is so expensive that i cannot afford it.
So i try to find another solution : my website is only aimed to the french people, so maybe is it possible to install a kind of firewall or proxy located before the server to block all the incoming IP adress not from france ? Do you know some websites who can do this and the price ?
I already try do deny the non-french ip in one htaccess file but the ddos attack saturate the server anyway.
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Jul 28, 2009
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.)
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May 3, 2009
someone decided to attack my webserver and I can't figure out how to block it.
tcp 0 0 localhost:80 207.44.129.88:2138 SYN_RECV
tcp 0 0 localhost:80 207.44.129.88:2243 SYN_RECV
tcp 0 0 localhost:80 213.66.121.211:63372 SYN_RECV
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.
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Jul 2, 2009
My server is currently underattack, I have been able to keep it up but after I ban 500 IPs, I get a lot of different IPs again.
Any idea or suggestion to do mass-ban to those attacking IPs?
tcp 0 0 xxx.xx.xxx.xxx:80 190.87.128.59:3965 SYN_RECV
tcp 0 0 xxx.xx.xxx.xxx:80 82.115.52.10:2323 SYN_RECV
tcp 0 0 xxx.xx.xxx.xxx:80 90.148.137.56:21094 SYN_RECV
tcp 0 0 xxx.xx.xxx.xxx:80 189.237.35.155:57605 ...
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Apr 1, 2009
i,m under attack i got in csf today this
77.195.42.235 # lfd: (PERMBLOCK) 77.195.42.235 has had more than 4 temp blocks in the last 86400 secs - Wed Apr 1 09:39:35 2009
151.60.86.210 # lfd: (PERMBLOCK) 151.60.86.210 has had more than 4 temp blocks in the last 86400 secs - Wed Apr 1 09:39:51 2009
and these two ips was attack me them down site for 2 minutes but then block in csf
so i just wanna ask now this option in CSF
LF_PERMBLOCK : 1
i make it open 1 so this the reason can block the ips attack. or this the reason make them can attack ?
so i should keep this option 1 or make it 0 to stop this kind of ddos attacking?
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Feb 4, 2008
Our forum is under attack...and our host won't do anything except tell us that our load is too high and that they might turn off our account.
But, we've already turned off the forum...the only load is a note that says it's down for maintenance...no database...no html...nothing.
In a very short amount of time it has has over 300,000 page requests for the same three pages.
Is there anything on my side (since I don't run the server) that I can do to stop this or prevent it...etc?
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