SYN attack, Unknown requests – Unknown IP Ranges – Not able to stop – Help us!

phpfreek2007 · July 15, 2009

Hi All,

For the last 6 months our site has been under severe brute force, syn flood attack. They keep bombarding a single URL of the server and it is xml file. They are not attacking any other URL.

e.g. http://www.example.com/rss123/attackedfilename.xml

We have removed the xml page from our site but still they keep on sending requests, this is for the last 6 months non stop.

The IP has been changed just to see and they are sending several thousand requests per second. The requests come from different IPS and different ranges, so you can not even block the IP’s. They seem to be coming from a legitimate IP’s.

Due to this I have had to pay for an extremely expensive server which holds 8 GB of RAM and quad core processor etc, however, even with this the server still reaches critical level, just because these requests are eating up my resources.

Our technical team has been working on all aspects of apache server security, external modules, firewall, hardware firewall from beginning but still we are not able to stop them.

We have installed following modules.

1) mod_security

2) mod_evasive

3) Firewall

We have worked with the hosting company and their technical team leader, he installed the best CISCO hardware firewall and tried to stop them, but in vain.

We have checked our server to see if anything from our site is causing the request, no extra file uploaded on to the server. For example if some file has been upload or some text has been added to the file (checked if we’ve been hacked). Even though we checked for any hacks, I am still wondering if there is something we do not know about. Can a hack lead to huge amounts of traffic?

We need some help to stop these attacks. We have searched a lot and have found that sites that get attacked like this have only one option is to shut down till it stops. I really hope that will not be the case for us. Please let us know if any one has any ideas to deal with this.

We are willing to try any small suggestion which might help from coding to scripting to modules to firewall. So please provide suggestion/solutions and way to get us out of this.

Also could it be our own part of php code which can do this? We are ready to check every php file to make sure it does not have any line of code which can be dangerous?

Thank you for your help in advance! Help!

Regards,

Sam

phpfreek2007 · July 16, 2009

Hi,

I just had a long meeting with my technical team and following are the updates.

1) SYN cookies is already Enable but not making much difference.

2) I will provide the packet details soon for the request to give the extra idea for the attack.

3) Following are the details I have got from my linux admin. This will help you to trace the issue in better way.

Problem: Apache SYN_RECV

OS - RHEL5

kernels - 2.6.18-92.1.22.el5-x86_64

2.6.18-92.el5-x86_64

rpms:-

kernel-devel-2.6.18-92.el5

kernel-headers-2.6.18-92.1.22.el5

kernel-devel-2.6.18-92.1.22.el5

kernel-2.6.18-92.1.22.el5

kernel-2.6.18-92.el5

OS Type:

cat /etc/issue

Red Hat Enterprise Linux Server release 5.2 (Tikanga)

> cat /proc/version

Linux version 2.6.18-92.1.22.el5 (mockbuild@hs20-bc2-5.build.redhat.com) (gcc version 4.1.2 20071124 (Red Hat 4.1.2-42)) #1 SMP Fri Dec 5 09:28:22 EST 2008

We are providing 403 code for the URL request. Following is part of Access Log

94.70.118.139 - - [11/Jun/2009:04:46:32 -0500] "GET /rss/test.xml HTTP/1.1" 403 292 "-" "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; FunWebProducts; SLCC1; .NET CLR 2.0.50727; Media Center PC 5.0; .NET CLR 3.0.04506; CT2077543_4.5.188.7)"

89.216.230.148 - - [11/Jun/2009:04:46:32 -0500] "GET /rss/test.xml HTTP/1.1" 403 292 "-" "Mozilla/5.0 (Windows; U; Windows NT 5.1; sr; rv:1.9.0.10) Gecko/2009042316 Firefox/3.0.10"

82.81.54.226 - - [11/Jun/2009:04:46:32 -0500] "GET /rss/test.xml HTTP/1.1" 403 292 "-" "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; GTB5; CT2077543_4.5.191.15)"

85.229.15.86 - - [11/Jun/2009:04:46:32 -0500] "GET /rss/test.xml HTTP/1.1" 403 292 "-" "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; GTB6; .NET CLR 2.0.50727; CT2088752_4.5.188.7)"

92.237.189.17 - - [11/Jun/2009:04:46:32 -0500] "GET /rss/test.xml HTTP/1.1" 403 292 "-" "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.10) Gecko/2009042316 Firefox/3.0.10"

84.106.127.218 - - [11/Jun/2009:04:46:32 -0500] "GET /rss/test.xml HTTP/1.1" 403 292 "-" "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; SLCC1; .NET CLR 2.0.50727; Media Center PC 5.0; eSobiSubscriber 2.0.4.16; OfficeLiveConnector.1.3; OfficeLivePatch.0.0; InfoPath.2; .NET CLR 3.5.30729; .NET CLR 3.0.30618; CT2088433_4.5.188.7)"

87.93.30.98 - - [11/Jun/2009:04:46:32 -0500] "GET /rss/test.xml HTTP/1.1" 403 292 "-" "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.0; Trident/4.0; GTB6; SLCC1; .NET CLR 2.0.50727; Media Center PC 5.0; .NET CLR 3.5.30729; .NET CLR 3.0.30618; CT2088347_4.5.188.7)"

93.86.61.247 - - [11/Jun/2009:04:46:32 -0500] "GET /rss/test.xml HTTP/1.0" 403 292 "-" "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; InfoPath.2; .NET CLR 2.0.50727; .NET CLR 3.0.04506.648; CT2077543_4.5.188.7)"

91.152.228.27 - - [11/Jun/2009:04:46:32 -0500] "GET /rss/test.xml HTTP/1.1" 403 292 "-" "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; GTB6; SLCC1; .NET CLR 2.0.50727; Media Center PC 5.0; .NET CLR 3.0.04506; OfficeLiveConnector.1.3; OfficeLivePatch.0.0; Creative ZENcast v2.00.13; CT2088347_4.5.188.7)"

94.69.164.32 - - [11/Jun/2009:04:46:32 -0500] "GET /rss/test.xml HTTP/1.1" 403 292 "-" "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; FunWebProducts; .NET CLR 1.1.4322; .NET CLR 2.0.50727; CT2088700_4.5.191.15)"

82.201.180.177 - - [11/Jun/2009:04:46:32 -0500] "GET /rss/test.xml HTTP/1.1" 403 292 "-" "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; GTB6; CT2077543_4.5.189.28)"

83.248.2.230 - - [11/Jun/2009:04:46:32 -0500] "GET /rss/test.xml HTTP/1.1" 403 292 "-" "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; SIMBAR={46BC3752-9118-483D-8E88-CD3E89FCD192}; GTB6; Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1) ; SLCC1; .NET CLR 2.0.50727; Media Center PC 5.0; .NET CLR 3.0.04506; CT2088752_4.5.188.7)"

99.235.137.30 - - [11/Jun/2009:04:46:32 -0500] "GET /rss/test.xml HTTP/1.1" 403 292 "-" "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; GTB6; .NET CLR 2.0.50727; OfficeLiveConnector.1.3; OfficeLivePatch.0.0; CT2077543_4.5.191.15)"

216.155.136.84 - - [11/Jun/2009:04:46:32 -0500] "GET /rss/test.xml HTTP/1.1" 403 292 "-" "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; SLCC1; .NET CLR 2.0.50727; .NET CLR 3.0.04506; .NET CLR 1.1.4322; CT2077543_4.5.188.7)"

217.123.166.205 - - [11/Jun/2009:04:46:32 -0500] "GET /rss/test.xml HTTP/1.1" 403 292 "-" "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; GTB5; Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1) ; SLCC1; .NET CLR 2.0.50727; Media Center PC 5.0; InfoPath.2; .NET CLR 3.5.30729; .NET CLR 3.0.30618; CT2088433_4.5.188.7)"

86.96.227.88 - - [11/Jun/2009:04:46:32 -0500] "GET /rss/test.xml HTTP/1.1" 403 292 "-" "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; GTB6; SLCC1; .NET CLR 2.0.50727; Media Center PC 5.0; .NET CLR 3.0.04506; CT2077543_4.5.188.7)"

203.115.189.77 - - [11/Jun/2009:04:46:32 -0500] "GET /rss/test.xml HTTP/1.1" 403 292 "-" "Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; CT2077543_1.5.48.2; rv:1.9.0.10) Gecko/2009042316 Firefox/3.0.10"

203.82.79.102 - - [11/Jun/2009:04:46:32 -0500] "GET /rss/test.xml HTTP/1.1" 403 292 "-" "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 2.0.50727; CT2088347_4.5.188.7)"

88.195.52.126 - - [11/Jun/2009:04:46:32 -0500] "GET /rss/test.xml HTTP/1.1" 403 292 "-" "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0; GTB6; SLCC1; .NET CLR 2.0.50727; Media Center PC 5.0; OfficeLiveConnector.1.3; OfficeLivePatch.0.0; .NET CLR 3.5.30729; .NET CLR 3.0.30618; CT2088347_4.5.189.24)"

77.81.114.171 - - [11/Jun/2009:04:46:32 -0500] "GET /rss/test.xml HTTP/1.1" 403 292 "-" "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; GTB6; SIMBAR={B471FCBA-22ED-11DE-91A3-00196693641D}; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.648; .NET CLR 3.5.21022; CT2077543_4.5.191.15)"

92.84.250.65 - - [11/Jun/2009:04:46:32 -0500] "GET /rss/test.xml HTTP/1.1" 403 292 "-" "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; CT2077543_4.5.191.15)"

netstat:

tcp 0 0 domain.com:http 85-156-91-20.elisa-mo:55168 SYN_RECV

tcp 0 0 domain.com:http 220.255.7.227:27183 SYN_RECV

tcp 0 0 domain.com:http 5e03cbc4.bb.sky.com:51086 SYN_RECV

tcp 0 0 domain.com:http 79.126.234.198:18139 SYN_RECV

tcp 0 0 domain.com:http 78.148.175.148:11115 SYN_RECV

tcp 0 0 domain.com:http 83-154-143-68.rev.lib:61479 SYN_RECV

tcp 0 0 domain.com:http ABTS-North-Static-248:54775 SYN_RECV

tcp 0 0 domain.com:http 90-230-131-95-no130.tb:1134 SYN_RECV

tcp 0 0 domain.com:http static-host119-73-6-2:49538 SYN_RECV

tcp 0 0 domain.com:http 222.127.130.238:gtp-control SYN_RECV

tcp 0 0 domain.com:http acl1-1571bts.gw.smartbr:g5m SYN_RECV

tcp 0 0 domain.com:http athedsl-282427.home.o:60002 SYN_RECV

tcp 0 0 domain.com:http CPE-58-166-77-138.nsw:60067 SYN_RECV

tcp 0 0 domain.com:http C-59-101-99-107.syd.c:51097 SYN_RECV

tcp 0 0 domain.com:http ti0111a380-2667.bb.on:60993 SYN_RECV

tcp 0 0 domain.com:http 92.81.2.242:60451 SYN_RECV

tcp 0 0 domain.com:http 118.100.120.248:pserver SYN_RECV

tcp 0 0 domain.com:http triband-del-59.178.84:50140 SYN_RECV

tcp 0 0 domain.com:http cpc4-leds5-0-0-cust82:obrpd SYN_RECV

tcp 0 0 domain.com:http ALyon-153-1-8-78.w86-:59494 SYN_RECV

tcp 0 0 domain.com:http 120.28.199.183:3comnetman SYN_RECV

tcp 0 0 domain.com:http h248.4.16.98.dynamic.:60758 SYN_RECV

tcp 0 0 domain.com:http 89.211.205.59:64217 SYN_RECV

tcp 0 0 domain.com:http CPE-124-187-26-30.qld:ff-sm SYN_RECV

tcp 0 0 domain.com:http frw.Gloworld.com:59104 SYN_RECV

tcp 0 0 domain.com:http 220.255.7.182:winpoplanmess SYN_RECV

tcp 0 0 domain.com:http srisaionline180.excell:1232 SYN_RECV

tcp 0 0 domain.com:http CPE-60-230-16-150.vic:52611 SYN_RECV

tcp 0 0 domain.com:http 203.82.91.102:41318 SYN_RECV

tcp 0 0 domain.com:http 69.171.165.50:32454 SYN_RECV

tcp 0 0 domain.com:http dsl-TN-static-195.:corbaloc SYN_RECV

tcp 0 0 domain.com:http 210.186.66.179:49330 SYN_RECV

tcp 0 0 domain.com:http ABTS-North-D:xinuexpansion3 SYN_RECV

tcp 0 0 domain.com:http c122-106-133-46.livrp:49273 SYN_RECV

tcp 0 0 domain.com:http 173.subnet125-1:nssalertmgr SYN_RECV

tcp 0 0 domain.com:http 121.246.52.30.dynamic:63977 SYN_RECV

tcp 0 0 domain.com:http mobile-3G-dyn-BC-179-1:4464 SYN_RECV

tcp 0 0 domain.com:http crd48.neoplus.adsl.t:aminet SYN_RECV

Following we have done till now is mentioned below for the configurations.

###############

sysctl.conf

##############

# Kernel sysctl configuration file for Red Hat Linux

#

# For binary values, 0 is disabled, 1 is enabled. See sysctl( and

# sysctl.conf(5) for more details.

# Controls IP packet forwarding

net.ipv4.ip_forward = 0

# Controls source route verification

net.ipv4.conf.default.rp_filter = 1

# Do not accept source routing

net.ipv4.conf.default.accept_source_route = 0

# Controls the System Request debugging functionality of the kernel

kernel.sysrq = 0

# Controls whether core dumps will append the PID to the core filename

# Useful for debugging multi-threaded applications

kernel.core_uses_pid = 1

# Controls the use of TCP syncookies

net.ipv4.tcp_syncookies = 1

# Controls the maximum size of a message, in bytes

kernel.msgmnb = 65536

# Controls the default maxmimum size of a mesage queue

kernel.msgmax = 65536

# Controls the maximum shared segment size, in bytes

kernel.shmmax = 68719476736

# Controls the maximum number of shared memory segments, in pages

kernel.shmall = 4294967296

net.ipv4.tcp_syncookies = 1

net.ipv4.tcp_synack_retries = 2

# Enable IP spoofing protection, turn on Source Address Verification

net.ipv4.conf.all.rp_filter = 1

# Enable TCP SYN Cookie Protection

net.ipv4.tcp_syncookies = 1

# 65536 seems to be the max it will take

net.ipv4.ip_conntrack_max = 1048576

net.ipv4.tcp_rmem = 4096 87380 8388608

net.ipv4.tcp_wmem = 4096 87380 8388608

net.core.rmem_max = 8388608

net.core.wmem_max = 8388608

net.core.netdev_max_backlog = 5000

net.ipv4.tcp_window_scaling = 1

#############

fwsnort, bfd burnintest chkrootkit ddos faf lsm nobody_check sim apf

#############

modsecurity-apache

LoadModule evasive20_module /usr/lib64/httpd/modules/mod_evasive20.so

DOSHashTableSize 3097

DOSPageCount 3

DOSSiteCount 50

DOSPageInterval 1

DOSSiteInterval 1

DOSBlockingPeriod 30

</IfModule>

LoadModule security_module /usr/lib64/httpd/modules/mod_security.so

DOSHashTableSize 3097

DOSPageCount 3

DOSSiteCount 50

DOSPageInterval 1

DOSSiteInterval 1

DOSBlockingPeriod 30

</IfModule>

####################

Again,

Hope this helps you to see the issue in details. I have also put the latest configurations to keep site going on.

If it may be where server has some maleware or spyware, please let me know the solution and we can scan the pc for that too. Besides these, please let me know for any suggestion you think will be helpful.

Thanks again for your time and have a wonderful day.

Sam

phpfreek2007 · July 17, 2009

Hi,

We have updated the firewall for few IP rules but in vain. Also 2-3 questions that have come to us are can it be a Virus or any malware which causes this?

We have the antivirus installed on our dedicated server and its saying server is fine, however, if needed we can try for new ones no matter for paid ones.

I am still doubting for any php code which can cause such things but I am not able to find anything regarding this.

however, we are trying and of anyone has any suggestion, please share them with us.

Thanks

Sam

trq · July 17, 2009

I fail to see what this has to do with Apache. If you can't get this sorted at the firewall, you have some real issues on your hands.

phpfreek2007 · July 18, 2009

Hi,

Ya, have a real problem but we will not to solve it. Any specific firewall you know which can stop URL specific request?

Unfortunately we are not able to find anything right now?

Sam

agallo · July 21, 2009

Any Cisco PIX hardware firewall should do the trick. You can set the number of max requests per host per second with any of their hardware firewall devices. PIX has been discontinued but if you are trying to save money is the best bet to find one used. This has resolved any issues with any kind of DOS attacks to my servers. If money is not an issue look into an Intrusion Prevention Sensor which has the ability to shun known signatures. The latest IOS for Cisco's ASAs is capable of preventing known signatures with a license fee. Hope this helps.

phpfreek2007 · July 22, 2009

Hi,

We tried CISCO Pix hardware firewall for 5 months however they are not able to stop the pattern at which they are blasting the site. I will look for the second option too since money is not an issue.

Can you please pass on more details for second and third option. Also following are updates i have done to server.

I Scanned the server with rootkit antispyware, no infection found. Regarding the firewall, put on BFD firewall over APF, still requests are not getting down.

Also IP table is getting full of new ips and it keeps network slow. Please advice.

Sam

trq · July 22, 2009

I'm sorry to say but through reading your posts, I'd say your pretty well f*cked. There doesn't seem to be much more you can do. I mean you've switched servers, switched ip's, have in place firewalls (both software and hardware based). What else is there?

Can you post the output of....

sudo iptables -L

?

steviewdr · July 23, 2009

Did you say several 1000's requests a second?

Why don't you do a connection rate limit on your firewall?

I.E. any ip (even a legitimate) can only establish a connection a certain amount of times a second.

How many unique IPs are accessing this at any one time?

You seem to be doing a lot of looking on this topic.

E.g. http://forums.devnetwork.net/viewtopic.php?f=34&t=103174&p=552885

I suggest you try the iptable rule mentioned there.

-steve

phpfreek2007 · July 25, 2009

Hi, Changing request per second is secondary solution. I want to stop those request touch my network, have tried those rules and verified but not getting any result.

Thanks and pls let me know for all the suggestion.

Sam

MyUser · August 7, 2009

CSF helps in those cases

Sign In

SYN attack, Unknown requests – Unknown IP Ranges – Not able to stop – Help us!

Recommended Posts

phpfreek2007

Link to comment

Share on other sites

phpfreek2007

Link to comment

Share on other sites

phpfreek2007

Link to comment

Share on other sites

trq

Link to comment

Share on other sites

phpfreek2007

Link to comment

Share on other sites

agallo

Link to comment

Share on other sites

phpfreek2007

Link to comment

Share on other sites

trq

Link to comment

Share on other sites

steviewdr

Link to comment

Share on other sites

phpfreek2007

Link to comment

Share on other sites

MyUser

Link to comment

Share on other sites

Join the conversation

Browse

Activity

Important Information