Has anyone noticed the site getting a lot more spam posts than usual over the past couple days? The ones I've seen repeatedly have "BingX referral codes" or similar codes for Bitcoin or other cryptocurrencies or something. Are the moderators aware of this problem? Is there something normal users can do to help?

EDIT: Something further I've noticed about this recent spate of spam bots is that they sometimes post in languages other than English (I've noticed Turkish in particular but I think there are several).

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    $\begingroup$ Flag as spam as soon as you see it. Enough flags and it gets deleted (and some other things happen behind the scenes). $\endgroup$
    – David Roberts Mod
    Apr 18 at 3:11
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    $\begingroup$ See also: What should I do when I see a spam post on MO? (Although one could say that this is briefly summarized by David Roberts' comment.) After the next update of SEDE one can use the database to see the number of spam posts - some similar queries can be found here: To which extent should spam posts on meta be considered a problem? And one could also check the stats available in metasmoke. $\endgroup$ Apr 18 at 11:41
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    $\begingroup$ @JosephVanName: While there is no obligation to comment when you vote to close, doing so and then making a comment like you did is very unprofessional. I would delete your comment if I were you. $\endgroup$ Apr 18 at 12:20
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    $\begingroup$ (I have also upvoted both this post and the answer to counteract what I presume are JvN’s vindictive downvotes) $\endgroup$ Apr 18 at 12:21
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    $\begingroup$ We're helping out also, doing all we can to flag as soon as possible. Yesterday alone, there was over 55 reported of those. $\endgroup$
    – Cow
    Apr 18 at 14:56
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    $\begingroup$ Thanks, @Cow . I also pointed to Charcoal on Alex's answer, before seeing that that was what you linked to. $\endgroup$
    – David Roberts Mod
    Apr 19 at 2:07
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    $\begingroup$ On the flip side, think about all the shiny new marshal badges. $\endgroup$ Apr 23 at 9:30

2 Answers 2


Yesterday (April 17th) the site was "under attack" between (approximately) 08:00 UTC and 11:00 UTC. During this period, I myself flagged 23 posts as spam. Besides downvoting and flagging as spam, there is nothing that can normal users can do.

IP-based blocking is not trustworthy, because spammers can use Tor or VPNs to hide their origin. On the other hand, moderators could, in principle, install keyword-based filters (for words like "coupon", "referral code", "bonus", "sign up"), so maybe they should step into this discussion and comment on this possibility. (Of course, such filters introduce the possibility of false positives, but for the list of words given above the probability of this happening should be very low.)

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    $\begingroup$ "moderators could, in principle, install keyword-based filters" - perhaps you'd be interested to see charcoal-se.org then :-) $\endgroup$
    – David Roberts Mod
    Apr 19 at 2:02
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    $\begingroup$ And see also stackoverflow.blog/2020/06/25/… $\endgroup$
    – David Roberts Mod
    Apr 19 at 2:05
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    $\begingroup$ Blacklisting coupon could be a nuisance because of questions about variants on the coupon collector's problem. There are three legit questions with that keyword just in the past month. $\endgroup$ Apr 19 at 9:05
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    $\begingroup$ I suspect “bonus” is also somewhat frequent (in phrases such as “bonus question”). $\endgroup$ Apr 19 at 12:33
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    $\begingroup$ The tendency to co-opt common phraseology into mathematical parlance with the intent of ‘capturing intuition’ may prove an obstacle here. $\endgroup$
    – Alec Rhea
    Apr 20 at 2:00
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    $\begingroup$ Is there a way to do an "n-strikes-blacklist" - so e.g. a post that uses each of "coupon", "bonus", and "referral" gets hit, but using just one of those is fine? $\endgroup$ Apr 20 at 5:04
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    $\begingroup$ @AlecRhea: Agreed, but I was thinking about these words being present in the titles, not the bodies of the questions. $\endgroup$
    – Alex M.
    Apr 20 at 7:21
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    $\begingroup$ Probably it is worth mentioning that some of the keywords mentioned above have been added to the watchlist by the Charcoal team. Of course, this is a volunteer project, independent from the internal Stack Exchange system. $\endgroup$ Apr 24 at 14:15

This answer is community wiki - feel free to edit it if you have some useful information to add.

In case somebody wants to have a look at some stats about spam - for example to compare the current situation with the situation in the past - you can have a look at metasmoke or you could use SEDE.

Some basic information about Charcoal, SmokeDetector and related projects: https://charcoal-se.org/

In metasmoke you can find various stats and details about posts which were caught by SmokeDetector or reported manually. (So this isn't necessarily the same as the list of post which have actually been flagged as spam.)

You can find the list of posts on MathOverflow and MathOverflow Meta. If you look at details of some posts, if there is a small red flag on the top left, you can find logs of flags by Charcoal users. Here is an example of a flag log. (It is certainly valuable that volunteers from the Charcoal project help with removing spams on various sites in this network, including MathOverflow.)

In SEDE, one can find spam flags in the Votes table, using VoteTypeId=12 - which denotes spam. There is also VoteTypeId=4 meaning offensive. In some of the queries below you can change parameters to switch the parameters deciding which VoteTypeId is used.)

You should keep in mind that SEDE is updated only once a week (on Sunday) - so the stats shown here do now count the most recent posts.

  • Number of spam posts per month: main and meta.
  • Number of spam posts (questions, answers) per year: main, meta.
  • Number of spam posts per day: main, meta. (You can change the parameters if you want to see a different date range.)
  • List of the posts flagged as spam between the two given dates: main, meta. (These queries return the links too - but only the users who can view the deleted posts will actually be able to get to the content of those posts, too.)

For example, from those queries we get 181 spam posts in April 2024, which is so far the highest number.


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    $\begingroup$ So if I'm reading the data correctly, the current month of April 2024 is indeed way above average in terms of number of spam posts on the main site. $\endgroup$ Apr 24 at 15:49
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    $\begingroup$ @SamHopkins Yes, that's correct. Data in SEDE are as of April 20 and it already shows more posts than in any of the previous months. (I plan to add the total number for April after the end of the months.) I wonder whether this is similar to what we would see if MO decides to leave the SE network. $\endgroup$ Apr 24 at 16:02

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