Security Basics mailing list archives
Re: statefull inspection FW and hackers
From: "ॐ aditya mukadam ॐ" <aditya.mukadam () gmail com>
Date: Fri, 22 Aug 2008 22:23:14 +0530
my take on SPI: Stateful inspection can be best understood with security zones/level. By default, most of the firewall dont allow anything to come from low security zone to high (ie lets say from internet to internal resources). This would mean that if internal user accesses internet his response will be blocked. This is not desirable because we donot want to keep on opening hole from internet to internal host on the firewall. We need some mechanism to allow this response/reply back to the internal user.SPI helps us to achieve it ! As mentioned in the thread and also to keep it simple, SPI maintains a state table of requests and opens the incoming requests for that connection !Rest all the requests from low security zone to high are denied (if not explicitly allowed) Thanks, Aditya Govind Mukadam On Thu, Aug 21, 2008 at 3:37 AM, Andrea Gatta <andrea.gatta () gmail com> wrote:
David, depending on the target OS, a FIN scan can reveal open ports. Basically an unsolliceted FIN packet will be: - ignored on an open port (RFC 793) - while on a closed port that will trigger a RST/ACK back In turn that will give to the attacker a way to understand what ports are actually available on the target. Things is, a FIN scan is not likelly to be seen and logged by a firewall which si not stateful. Andrea On Wed, Aug 20, 2008 at 6:15 PM, David Gillett <gillettdavid () fhda edu> wrote:Statefulness doesn't help with SYN port scans -- that much is correct. However, some attacks may depend on violating the normal state transitions or sequencing of TCP traffic, or on scanning with other sorts of packets -- I see unsolicited SYN-ACK packets all the time. (Those are probably just responses to spoofed SYNs, but I can't know that for certain. I'm not sure what a scan with RST or FIN packets would reveal.) Most of the stateful firewalls I've seen also do inspection of FTP control traffic, so that FTP data sessions on negotiated ports can be allowed without leaving masses of high-numbered ports open all the time. An awful lot of junk/noise can be filtered out by that. David Gillett-----Original Message----- From: listbounce () securityfocus com [mailto:listbounce () securityfocus com] On Behalf Of Juan B Sent: Tuesday, August 19, 2008 10:05 PM To: security basics Subject: statefull inspection FW and hackers Hi, Can someone please explain why statefull inspection Fw helps against hackers? I know that those FW keep track of the sessions but I dont understand how the feature might help against a port scan from the internet or other ways to mitigate hackers attacks. Thanks Juan
Current thread:
- statefull inspection FW and hackers Juan B (Aug 20)
- Re: statefull inspection FW and hackers Adam Mooz (Aug 20)
- Re: statefull inspection FW and hackers Roman Fulop (Aug 20)
- RE: statefull inspection FW and hackers David Gillett (Aug 20)
- Re: statefull inspection FW and hackers Andrea Gatta (Aug 21)
- Re: statefull inspection FW and hackers ॐ aditya mukadam ॐ (Aug 25)
- Re: statefull inspection FW and hackers Andrea Gatta (Aug 21)
- Re: statefull inspection FW and hackers Andrea Gatta (Aug 20)
- Re: statefull inspection FW and hackers Adriel Desautels (Aug 20)
- <Possible follow-ups>
- Re: statefull inspection FW and hackers aditya . mukadam (Aug 25)