RE: Real-Time Mitigation of Denial of Service Attacks Now Available With AT&T
Because there are legitimate reasons for async routing. DirectPC/Isat/etc. (Satelite based services) come to mind immediately. Customers dial-up to an ISP and downstream traffic returns via the sat connection. Reverse-path immediately disables every one of these customers. Qwest deployed this on us with no notice and killed off thousands of customers in one fell swoop. Although I agree with the principal, the implentation needs more thought than a simple 'turn it on for 100%'. Eric Krichbaum -----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu] On Behalf Of Alexei Roudnev Sent: Thursday, June 03, 2004 1:40 AM To: Jon R. Kibler; nanog@merit.edu Subject: Re: Real-Time Mitigation of Denial of Service Attacks Now Available With AT&T You even do not need to maintain ACL - many routers have 'back-path verification' feature. I wonder, why DSL and other 'consumer level' providers are not doing it for 100% of their customers. ----- Original Message ----- From: "Jon R. Kibler" <Jon.Kibler@aset.com> To: <nanog@merit.edu> Sent: Wednesday, June 02, 2004 8:25 AM Subject: Re: Real-Time Mitigation of Denial of Service Attacks Now Available With AT&T
John Obi wrote:
... since DDoS is the nightmare of the internet now.
The sad fact is that simple ingress and egress filtering would eliminate the majority of bogus traffic on the Internet -- including (D)DoS attacks. If all ISPs would simply drop all outbound packets whose source address is not a valid IP for the subnet of origin, and all inbound packets that do not have valid source IP addresses, the DDoS problem would be (for all intents and purposes) fixed. If proper filtering was done, then any DoS attacks would have to have either valid source IP addresses, or IP addresses that spoofed IPs within their network of origin. In either case, identifying and shutting down the attackers would become a greatly simplified task compared to the mess it is today.
Why no filtering by ISPs? "Because it takes resources and only benefits the other guy" -- unless your network is the one under attack.
Maintenance of the ACLs should not be the issue. A single ACL for each subnet would be all that would be required for egress filtering. About 30 ACLs on an inbound border router would be required for ingress filtering. Keeping the ingress ACLs current is a brain-dead task -- just subscribe to the bogon mailing list at cymru.com.
ACLs have had a bad reputation for greatly slowing down routers. That may have been true in the past, but properly written ACLs do not seem to have a significant impact on most new routers. Yes, they may cut peak through-put a few percent -- but if you are running that close to the edge, it is time to upgrade anyway.
IMHO, there is absolutely no excuse for not doing ingress and egress filtering. In fact, if you are an ISP, I would argue that you are negligent in your fiduciary responsibilities to your customers and shareholders if you are not filtering source IP addresses.
Fancy solutions may make great marketing, but simple proper router filtering is a very workable lower-cost solution.
(Step down from soap box.) At least, that's my $0.02 worth.
Jon Kibler -- Jon R. Kibler Chief Technical Officer A.S.E.T., Inc. Charleston, SC USA (843) 849-8214
================================================== Filtered by: TRUSTEM.COM's Email Filtering Service http://www.trustem.com/ No Spam. No Viruses. Just Good Clean Email.
This is an interestig example - looks as some protocol, saying _these are my legal SRC addresses_, desired on customer's link. ======================================================== Because there are legitimate reasons for async routing. DirectPC/Isat/etc. (Satelite based services) come to mind immediately. Customers dial-up to an ISP and downstream traffic returns via the sat connection. Reverse-path immediately disables every one of these customers. Qwest deployed this on us with no notice and killed off thousands of customers in one fell swoop. Although I agree with the principal, the implentation needs more thought than a simple 'turn it on for 100%'. Eric Krichbaum -----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu] On Behalf Of Alexei Roudnev Sent: Thursday, June 03, 2004 1:40 AM To: Jon R. Kibler; nanog@merit.edu Subject: Re: Real-Time Mitigation of Denial of Service Attacks Now Available With AT&T You even do not need to maintain ACL - many routers have 'back-path verification' feature. I wonder, why DSL and other 'consumer level' providers are not doing it for 100% of their customers. ----- Original Message ----- From: "Jon R. Kibler" <Jon.Kibler@aset.com> To: <nanog@merit.edu> Sent: Wednesday, June 02, 2004 8:25 AM Subject: Re: Real-Time Mitigation of Denial of Service Attacks Now Available With AT&T
John Obi wrote:
... since DDoS is the nightmare of the internet now.
The sad fact is that simple ingress and egress filtering would eliminate the majority of bogus traffic on the Internet -- including (D)DoS attacks. If all ISPs would simply drop all outbound packets whose source address is not a valid IP for the subnet of origin, and all inbound packets that do not have valid source IP addresses, the DDoS problem would be (for all intents and purposes) fixed. If proper filtering was done, then any DoS attacks would have to have either valid source IP addresses, or IP addresses that spoofed IPs within their network of origin. In either case, identifying and shutting down the attackers would become a greatly simplified task compared to the mess it is today.
Why no filtering by ISPs? "Because it takes resources and only benefits the other guy" -- unless your network is the one under attack.
Maintenance of the ACLs should not be the issue. A single ACL for each subnet would be all that would be required for egress filtering. About 30 ACLs on an inbound border router would be required for ingress filtering. Keeping the ingress ACLs current is a brain-dead task -- just subscribe to the bogon mailing list at cymru.com.
ACLs have had a bad reputation for greatly slowing down routers. That may have been true in the past, but properly written ACLs do not seem to have a significant impact on most new routers. Yes, they may cut peak through-put a few percent -- but if you are running that close to the edge, it is time to upgrade anyway.
IMHO, there is absolutely no excuse for not doing ingress and egress filtering. In fact, if you are an ISP, I would argue that you are negligent in your fiduciary responsibilities to your customers and shareholders if you are not filtering source IP addresses.
Fancy solutions may make great marketing, but simple proper router filtering is a very workable lower-cost solution.
(Step down from soap box.) At least, that's my $0.02 worth.
Jon Kibler -- Jon R. Kibler Chief Technical Officer A.S.E.T., Inc. Charleston, SC USA (843) 849-8214
================================================== Filtered by: TRUSTEM.COM's Email Filtering Service http://www.trustem.com/ No Spam. No Viruses. Just Good Clean Email.
participants (2)
-
Alexei Roudnev -
Krichbaum, Eric