FWIW I have seen the captchas more often on IPv6 both from home and the office
than when both networks were using a single shared IPv4; not sure if this is
just related to chronology or a real effect. Once a month or so I seem to get
them for a couple of days, then they go away.
No idea what's triggering it. It would be *really* helpful if Google could
provide some useful technical details beyond a generic FAQ page. As it is I
just get annoyed by it and have no way to troubleshoot or correct the constant
false positives. How is Google detecting "robots"? My sense is that I tend to
trigger the captcha thing when iterating similar search terms (particularly due
to removal of the + operator and extremely poor "change my search terms because
you think you know better than I do what I want to search for" behaviour. My
search patterns haven't really changed since turning up IPv6 everywhere, so I
have to think either the captcha trigger has gotten more aggressive, or somehow
prefers to blacklist IPv6 users.
In any case, just going to IPv6 is definitely not a complete fix for this. It
seems to be related to search behaviour and $blackbox_magic.
Keenan Tims
Stargate Connections
________________________________________
From: NANOG <nanog-boun...@nanog.org> on behalf of Philip Lavine via NANOG
<nanog@nanog.org>
Sent: February 29, 2016 7:53 AM
To: Damian Menscher
Cc: nanog@nanog.org
Subject: Re: google search threshold
I have about 2000 users behind a single NAT. I have been looking at netflow,
URL filter logs, IDS logs, etc. The traffic seems to be legit.
I am going to move more users to IPv6 and divide some of the subnets into
different NATS and see if that alleviates the traffic load.
Thanks for the advice.
-Philip
From: Damian Menscher <dam...@google.com>
To: Philip Lavine <source_ro...@yahoo.com>
Cc: "nanog@nanog.org" <nanog@nanog.org>
Sent: Friday, February 26, 2016 6:05 PM
Subject: Re: google search threshold
On Fri, Feb 26, 2016 at 3:01 PM, Philip Lavine via NANOG <nanog@nanog.org>
wrote:
Does anybody know what the threshold for google searches is before you get the
captcha?I am trying to decide if I need to break up the overload NAT to a pool.
There isn't a threshold -- if you send automated searches from an IP, then it
gets blocked (for a while).
So... this comes down to how much you trust your machines/users. If you're a
company with managed systems, then you can have thousands of users share the
same IP without problems. But if you're an ISP, you'll likely run into
problems much earlier (since users like their malware).
Some tips: - if you do NAT: try to partition users into pools so one abusive
user can't get all your external IPs blocked - if you have a proxy: make sure
it inserts the X-Forwarded-For header, and is restricted to your own users -
if you're an ISP: IPv6 will allow each user to have their own /64, which avoids
shared-fate from abusive ones
Damian (responsible for DDoS defense)-- Damian Menscher :: Security Reliability
Engineer :: Google :: AS15169
