RE: DoS problem.



Call the ISP, they can usually isolate it from there...


-----Original Message-----
From: Jorge Alfredo Garcia [mailto:frederix@xxxxxxxxx]
Sent: 20 January 2006 18:02
To: pen-test@xxxxxxxxxxxxxxxxx; firewalls@xxxxxxxxxxxxxxxxx
Subject: DoS problem.

I have two dedicated servers, both hosted by the same provider and
both on the same segmnet.
I am under a denial of services attack but idont know exactaly how to
stop it.
Here is a piece of my netstat output:

tcp 0 1 XX.XX.XX.AA:47561 XX.XX.XX.BB:80
SYN_SENT
tcp 0 1 XX.XX.XX.AA:47562 XX.XX.XX.BB:80
SYN_SENT
tcp 0 1 XX.XX.XX.AA:47565 XX.XX.XX.BB:80
SYN_SENT
tcp 0 1 XX.XX.XX.AA:47564 XX.XX.XX.BB:80
SYN_SENT
tcp 0 1 XX.XX.XX.AA:47567 XX.XX.XX.BB:80
SYN_SENT

Ok, XX.XX.XX.AA is the server i am in now.
XX.XX.XX.BB is mine two and here are the connections:

tcp 0 0 XX.XX.XX.BB:80 XX.XX.XX.AA:50749
SYN_RECV
tcp 0 0 XX.XX.XX.BB:80 XX.XX.XX.AA:50598
SYN_RECV
tcp 0 0 XX.XX.XX.BB:80 XX.XX.XX.AA:50309
SYN_RECV

I have thousands of this connections on both servers.
I make iptables rules in both sites but the attack still running and
the rules dont work.

I cant understand how this attack can be made taking into account that
the attacker isnt inside any of my servers.
Why iptables rules dont work against this?

Thanx in advance.

______________________________________________________________________

This email has been scanned by the MessageLabs Email Security System.
______________________________________________________________________

Visit us at http://www.aggreko.com

Confidentiality Notice: This communication and any accompanying attachments contain confidential information intended for a specific individual and purpose. This communication is private and protected by law. If you are not the intended recipient, you are hereby respectfully notified that any disclosures, copying, forwarding or distribution, or the taking of any action based on the contents of this communication is strictly prohibited.

_____________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please visit http://www.messagelabs.com/email
______________________________________________________________________

------------------------------------------------------------------------------
Audit your website security with Acunetix Web Vulnerability Scanner:

Hackers are concentrating their efforts on attacking applications on your
website. Up to 75% of cyber attacks are launched on shopping carts, forms,
login pages, dynamic content etc. Firewalls, SSL and locked-down servers are
futile against web application hacking. Check your website for vulnerabilities
to SQL injection, Cross site scripting and other web attacks before hackers do!
Download Trial at:

http://www.securityfocus.com/sponsor/pen-test_050831
-------------------------------------------------------------------------------



Relevant Pages

  • Re: Port 80 SYN flood-like behavior
    ... > were on the receiving end of such an attack a little over one month ago. ... > across a LARGE number of TCP servers. ... > SYN/ACK packets ... ... Traffic reflection off routers ...
    (Incidents)
  • [REVS] DNS Amplification Attacks
    ... DNS Amplification Attacks ... One of the networks under attack indicated some ... exploited name servers. ...
    (Securiteam)
  • Analysis of SSH crc32 compensation attack detector exploit
    ... Analysis of SSH crc32 compensation attack detector exploit ... detector vulnerability to remotely compromise a Red Hat Linux ... Active Internet connections (servers and established) ...
    (Incidents)
  • Re: Strange DoS / new halflife server bug? (Update)
    ... misconfigured/old versions of halflife servers. ... The public available exploits CANNOT create this attack. ... service attack (e.g. read possible vulnerable servers from a file). ... > world's premier technical IT security event! ...
    (Incidents)
  • Re: What is a Denial of Service Attack?
    ... All resources (whether they are web servers, dns servers, file servers ... Denial of Service attack. ... Most often, the requests come from, or pretend to come from, different ... The SYN flag set in each packet is a request to open a new connection ...
    (comp.security.firewalls)