[x]
Posted via EE Mobile

Search, ask, and monitor your questions on the go with EE Mobile. Visit Experts Exchange from your mobile device and never be out of touch again.
12/04/2005 at 05:21PM PST, ID: 21652753
[x]
Attachment Details
[x]
The Solution Rating System

With so many solutions, how can you tell which solutions are most likely to help you and which ones are not? To provide you with a tool to use, we rate our solutions based on various elements that most accurately determine if a solution is a quality solution. To explain what factors affect the solution rating, here are the elements we take into consideration when formulating our solution rating.

  • The Grade of the Solution
  • The Zone Rank of the Expert Providing the Solution
  • The Number of Author and Expert Comments
  • The Number of Experts Contributing
  • The Feedback of the Community

Your Input Matters
Because of the way the system is set up, the most important variable in this equation is you. As a member of Experts Exchange, you are able to cast your vote on the quality of the solutions in regard to how complete, accurate, helpful and easy to understand each solution is. When you provide your feedback, each rating is adjusted accordingly. So, if you see a solution that has a poor rating that you think is a good solution, let us know by rating it. As you do, the rating will be adjusted and will become more accurate for other members of our site.

If you have any suggestions that you would like to make for our rating system, please ask a question in the Suggestions Zone of Community Support.

Thank you!
8.6

Syn Flood causing snort overload at firewall / IPS

Asked by dracocat in Miscellaneous Networking, Network Operations, Consumer Firewalls

Tags: syn

Our servers are being attacked by a syn flood to TCP port 80.
The source address on each packet is from a random source address.
All other information including TTL and Window size appears to be random as well, so it is difficult to pick out any sort of packet signature.

If the webserver (running Debian) is placed in front of the firewall, and tcp_syncookies is enabled, then the system is able to cope with the syn flood without incident.

When placed behind the firewall (Astaro Security Linux), the firewall servers CPU maxes out, and a look at top shows that it is 80% snort, and 20% logging.  We did pay for the platinum tech support with Astaro, but it seems they are not aware of this issue.

I am able to duplicate this attack using the source from juno.c and find that the CPU just maxes out at 1.68 Mbit or 3503 packets per second; the attacker is attacking at 8Mbit, and our pipe is 100 Mbit so in the future it could be potentially even more.

Because of credit card regulations, our servers must be behind a firewall and IPS.

How on earch can we stop this idiot without buying 10 firewalls to spread the load just in case we get a syn flood?

--------
Some ideas I have had:
Is it possible to allow TCP SYN packets to bypass snort and the IDS as these are assumbably harmless?
I have been pointed in the direction of using netflow and reverse AS Path checking.  Is this even possible with a single home?
Is there some sort of device that can be placed in front of the firewall that can filter this traffic out?
Lastly, is there some sort of device that we could place in front of the firewall that does nothing but proxy syn/syn-ack handshaking?


Thanks a bunch!
(If you are in the L.A. area and want some consulting work on this let me know as well).

[+][-]12/04/05 06:05 PM, ID: 15416816

At Experts Exchange, members can ask their questions to thousands of technology professionals, also known as Experts. Experts compete and collaborate to answer those questions by leaving comments like this one.

Start your 30-day free trial to view this Expert Comment or ask the Experts your question.

 
[+][-]12/04/05 10:20 PM, ID: 15417605

Often, when Experts are collaborating with members who have asked questions, they will request additional information about the problem. Askers respond with an author comment like this one.

Start your 30-day free trial to view this Author Comment or ask the Experts your question.

 
[+][-]12/05/05 08:00 AM, ID: 15420242

At Experts Exchange, members can ask their questions to thousands of technology professionals, also known as Experts. Experts compete and collaborate to answer those questions by leaving comments like this one.

Start your 30-day free trial to view this Expert Comment or ask the Experts your question.

 
[+][-]12/07/05 12:05 AM, ID: 15434390

Often, when Experts are collaborating with members who have asked questions, they will request additional information about the problem. Askers respond with an author comment like this one.

Start your 30-day free trial to view this Author Comment or ask the Experts your question.

 
[+][-]12/07/05 07:32 AM, ID: 15436736

View this solution now by starting your 30-day free trial. Setting up your free trial is quick, easy, and secure. We will return you to this solution, unlocked, when you're done.

 

About this solution

Zones: Miscellaneous Networking, Network Operations, Consumer Firewalls
Tags: syn
Sign Up Now!
Solution Provided By: giltjr
Participating Experts: 2
Solution Grade: B
 
 
[+][-]12/07/05 03:23 PM, ID: 15440822

At Experts Exchange, members can ask their questions to thousands of technology professionals, also known as Experts. Experts compete and collaborate to answer those questions by leaving comments like this one.

Start your 30-day free trial to view this Expert Comment or ask the Experts your question.

 
[+][-]12/07/05 04:33 PM, ID: 15441348

At Experts Exchange, members can ask their questions to thousands of technology professionals, also known as Experts. Experts compete and collaborate to answer those questions by leaving comments like this one.

Start your 30-day free trial to view this Expert Comment or ask the Experts your question.

 
 
Loading Advertisement...
20090824-EE-VQP-74