Penetration Testing mailing list archives
RE: Are Fragmentation Attacks Still Used for IDS/IPS Evasion?
From: "Philippe Bogaerts" <xxradar () radarhack com>
Date: Wed, 26 Sep 2007 17:54:11 +0200
Hi, I've seen some firewalls that support inspection of fragmented traffic, but it does not mean they reassemble the traffic. This should be done at the endpoint (host or server, or proxy). I agree that it becomes more difficult to 'fool' firewalls or IPS/IDS with fragmentation, but myself I had a lot of success with fragroute to bypass IDS/IPS systems that were able to decrypt SSL traffic. Very few (not to say none ...) were able to handle fragroute. If they already succeeded to support IP fragmentation, they certainly messed up when using the TCP segmentation features present in fragroute. Regards, Xxradar http://www.Radarhack.Com -----Original Message----- From: listbounce () securityfocus com [mailto:listbounce () securityfocus com] On Behalf Of Harry Hoffman Sent: Wednesday, September 26, 2007 4:36 AM To: seclt yuri Cc: pen-test () securityfocus com Subject: Re: Are Fragmentation Attacks Still Used for IDS/IPS Evasion? well, there are a few things to think about... fragmentation as DOS attacks, fragmentation as cover for stealth attacks, incorrectly configured firewalls, compromised systems on the inside that have a greater level of access then on the outside. (internal servers that are separated from Desktops from a router and not a firewall... not all that uncommon, unfortunately). Cheers, Harry seclt yuri wrote:
Yes but this effectively means that fragmentation attacks are useless if launched across the 'Net and when performing a penetration test without local access. Also, even internal host systems are usually segregated from servers and server vlans by a firewall, so even then, I can't see how fragmentation attacks would be effective. The only scenario that I can think of would be within the same subnet or vlan where traffic doesn't pass through a firewall. Please correct me if I am wrong. Thank you. --- Harry Hoffman <hhoffman () ip-solutions net> wrote:yep, unfortunately not enough people using host based firewalls and alot of attacks happen inside of where the firewall protects (i.e. local lan) seclt yuri wrote:Hi, I was just reading up on fragmentation attacksusingfragrouter and fragrouter as a mean of IDS/IPS evasion. However, since almost all firewalls both commercial and free (iptables for examples) nowhavesupport for fragment reassembly, are fragmentation attacks still effective? Thanks.
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Current thread:
- Are Fragmentation Attacks Still Used for IDS/IPS Evasion? seclt yuri (Sep 25)
- Re: Are Fragmentation Attacks Still Used for IDS/IPS Evasion? Harry Hoffman (Sep 25)
- Re: Are Fragmentation Attacks Still Used for IDS/IPS Evasion? seclt yuri (Sep 25)
- Re: Are Fragmentation Attacks Still Used for IDS/IPS Evasion? Harry Hoffman (Sep 25)
- RE: Are Fragmentation Attacks Still Used for IDS/IPS Evasion? Philippe Bogaerts (Sep 26)
- RE: Are Fragmentation Attacks Still Used for IDS/IPS Evasion? Shenk, Jerry A (Sep 26)
- RE: Are Fragmentation Attacks Still Used for IDS/IPS Evasion? xxradar (Sep 26)
- Re: Are Fragmentation Attacks Still Used for IDS/IPS Evasion? seclt yuri (Sep 25)
- Re: Are Fragmentation Attacks Still Used for IDS/IPS Evasion? Harry Hoffman (Sep 25)
- <Possible follow-ups>
- Re: Re: Are Fragmentation Attacks Still Used for IDS/IPS Evasion? vijay . upadhyaya (Sep 30)
- Re: Are Fragmentation Attacks Still Used for IDS/IPS Evasion? seclt yuri (Sep 30)