Re: ISP port blocking practice

[Zhiyun Qian <zhiyunq () umich edu>]

I skimmed through these specs. They are useful but seems only related specific to IP spoofing prevention. I see that IP 
spoofing is part of the asymmetric routing story. But I was more thinking that given that IP spoofing is not widely 
adopted, the other defenses that they can more perhaps more easily implement is to block incoming traffic with source 
port 25 (if they already decided to block outgoing traffic with destination port 25). But according to our study, most 
of the ISPs didn't do that at the time of study (probably still true today).

-Zhiyun
On Sep 2, 2010, at 9:20 PM, Suresh Ramasubramanian wrote:

> BCP38 / RFC2827 were created specifically to address some quite
> similar problems.  And googling either of those two strings on nanog
> will get you a lot of griping and/or reasons as to why these aren't
> being more widely adopted :)
>
> --srs
>
> On Fri, Sep 3, 2010 at 7:47 AM, Zhiyun Qian <zhiyunq () umich edu> wrote:
> > Suresh, thanks for your interest. I see you've had a lot of experience in fighting spam, so you must have known 
> > this. Yes, I know this spamming technique has been around for a while. But it's surprising to see that the majority 
> > of the ISPs that we studied are still vulnerable to this attack.  That probably indicates that it is not as widely 
> > known as we would expect. So I thought it would be beneficial to raise the awareness of the problem.
> >
> > In terms of more results, the paper is the most detailed document we have. Otherwise, if you interested in the data 
> > that we collected (which ISPs or IP ranges are vulnerable to this attack). We can chat offline.
> >
> > Regards.
> > -Zhiyun