I've posted answers from my mobile phone (iPhone 4S) fairly regularly over the past three months. In the past week, though, I've gotten the CAPTCHA on nearly every single answer I've posted from my phone. Before this week, I don't believe I had ever had to go through the verification.

Has anything changed in the detection algorithm recently or am I just unlucky?

  • It done did it to me too this evening
    – voretaq7
    Jan 31, 2012 at 2:28

2 Answers 2


Nope, no recent changes to the algorithm. You're just lucky (or unlucky, depending on how you look at it).

  • Okay, good to know. Thanks Anna.
    – EEAA
    Feb 2, 2012 at 3:56
  • 2
    @ErikA I checked into what happened. You changed IP addresses a few times right when starting your answers, which looks to have prevented certain spam prevention measures from completing. As Anna said, you were just lucky :) Feb 2, 2012 at 4:25
  • Thanks Jarrod, it makes sense how that could create issues. I suppose Verizon could be doing some creative routing or possibly I was just flopping back and forth between wifi and cellular data.
    – EEAA
    Feb 2, 2012 at 4:49

It appears that the detection algorithm tends to kick in whenever the IP address changes mid-session. If your provider uses NAT and rotating public IP assignment (seen this a couple of times with some providers), you might run into the issue more often than others.

  • Ah, I see it has been stated already that this is the root of the problem. My bad, I should have read the comments beforehand :=|
    – the-wabbit
    Feb 7, 2012 at 8:10

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