this post was submitted on 20 Jun 2023
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Admins, we're about to have a really bad SPAM problem when Lemmy removes captcha support in v.0.18 - You ALL have a responsibility to communicate back to lemmy devs to try to stop it. (tucson.social)
submitted 1 year ago* (last edited 1 year ago) by th3raid0r@tucson.social to c/technology@beehaw.org
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Look, we can debate the proper and private way to do Captchas all day, but if we remove the existing implementation we will be plunged into a world of hurt.

I run tucson.social - a tiny instance with barely any users and I find myself really ticked off at other Admin's abdication of duty when it comes to engaging with the developers.

For all the Fediverse discussion on this, where are the github issue comments? Where is our attempt to convince the devs in this.

No, seriously WHERE ARE THEY?

Oh, you think that just because an "Issue" exists to bring back Captchas is the best you can do?

NO it is not the best we can do, we need to be applying some pressure to the developers here and that requires EVERYONE to do their part.

The Devs can't make Lemmy an awesome place for us if us admins refuse to meaningfully engage with the project and provide feedback on crucial things like this.

So are you an admin? If so, we need more comments here: https://github.com/LemmyNet/lemmy/issues/3200

We need to make it VERY clear that Captcha is required before v0.18's release. Not after when we'll all be scrambling...

EDIT: To be clear I'm talking to all instance admins, not just Beehaw's.

UPDATE: Our voices were heard! https://github.com/LemmyNet/lemmy/issues/3200#issuecomment-1600505757

The important part was that this was a decision to re-implement the old (if imperfect) solution in time for the upcoming release. mCaptcha and better techs are indeed the better solution, but at least we won't make ourselves more vulnerable at this critical juncture.

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[–] xtremeownage@lemmyonline.com 7 points 1 year ago (23 children)

Hunh.

I just had a surge of user registrations on my instance.

All passed the captcha. All passed the email validation.

All, had a valid-sounding response.

I am curious to know if they are actual users, or.... if I just became the host of a spam instance. :-/

Doesn't appear to be an easy way to determine.

[–] th3raid0r@tucson.social 9 points 1 year ago (17 children)

Hmmm, I'd check the following:

  1. Do the emails follow a pattern? (randouser####@commondomain.com)
  2. Did the emails actually validate, or do you just not see bouncebacks? There is a DB field for this that admins can query (i'll dig it up after I make this high level post)
  3. Did the surge come from the same IP? Multiple? Did it use something that doesn't look like a browser?
  4. Did the surge traffic hit /signup or did it hit /api/v3/register exclusively?

With those answers I should be able to tell if it's the same or similar attacker getting more sophisticated.

Some patterns I noticed in the attacks I've received:

  1. it's exactly 9 attempts every 30 minutes from the user agent "python/requests"
  2. The users that did not get an email bounceback were still not authenticated hours later (maybe the attacker lucked out with a real email that didn't bounce back?). There was no effort to verify from what I could determine.

Some vulnerabilities I know that can be exploited and would expect to see next:

  1. ChatGPT is human enough sounding for the registration forms. I've got no idea why folks think this is the end-all solution when it could be faked just as easily.
  2. Duplicate Email conflicts can be bypassed by using a "+category" in your email. ie (someuser+lemmy@somedomain.com) This would allow someone to associate potentially hundreds of spam accounts with a single email.
[–] idealium@beehaw.org 2 points 1 year ago

ChatGPT is human enough sounding for the registration forms. I've got no idea why folks think this is the end-all solution when it could be faked just as easily.

A simple deterrent for this could be to "hide" some information in the rules and request that information in the registration form. Not only are you ensuring that your users have at least skimmed the rules, you're also raising the bar of difficulty for spammers using LLMs to generate human-sounding applications for your instance. Granted it's only a minor deterrent, this does nothing if the adversary is highly motivated, but then again the same can be said of a lot of anti-spammer solutions. :)

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