What is the correct way to handle spam on MathOverflow? Can regular users do something when they see a spam post?

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    $\begingroup$ I have created this post partially because sometimes I have seen users reacting to spam in an unusual way (or at least differently from the recommendations in the FAQ). To name just one example, a tag called (spam) was created a few times in the past. See also recent conversation in chat related to spam. $\endgroup$ Commented Jun 12, 2019 at 16:41
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    $\begingroup$ For these reasons I thought that it might be useful to have some basic info also on meta, not just in the help center (where they are mentioned very briefly) and in the network-wide FAQ. $\endgroup$ Commented Jun 12, 2019 at 16:42

1 Answer 1


Any user with at least 15 reputation points should flag the post as spam. After 6 spam flags, the post is deleted. In addition to being deleted, even for users who can see the deleted posts, the content of the post is hidden - although they can still access the revision history. The same thing happens after a total of 6 flags that are either "spam", or "rude or abusive".

A detailed network-wide FAQ about spam can be found on Meta Stack Exchange: What are the “spam” and “rude or abusive” (offensive) flags, and how do they work? That link, together with some additional links, can be found in the spam tag-info on this meta.

Some additional remarks:

  • Spam flags should be only used for posts that really contain spam. (A post is considered spam only if it advertises a product, service, or similar and is either or both unsolicited or lacks disclosure that the user is affiliated with the product/company/linked site/etc. This is elaborated in more detail in the network-wide FAQ.)
  • A spam flag automatically adds a downvote, so it's not necessary to downvote the post in addition to that. See also: Why shouldn't I downvote spam that I've already flagged?
  • Also voting to close (or to delete) is not really necessary - it is likely that 6 users with 15 reputation points get to the post quicker than 5 users who have enough reputation to cast close votes. Of course, this assumes that the users know how to handle spam posts. Voting to close, when done in addition to flagging as spam doesn't cause any harm, other than spending one of your close-votes. It is better not to vote to delete. If the post is deleted by votes rather than by spam flags, it's good to notify moderators about this. For more details, see: Should we vote to delete spam posts?
  • Editing the spam content out can be counterproductive - since other users who see the same post might not realize the it is spam. It's also possible that the spam post will be seen as a real post and end up giving the spammer significant reputation. On one Stack Exchange site, there's even been one edited spam question from a repeat spammer that got answers and made it onto the Hot Network Questions list. The spammer getting reputation makes it significantly harder to deal with their subsequent spam, as many of the automated checks for spam are bypassed for users with even a moderate amount of reputation. See also: Should spam posts be edited?

So, basically, it can be said that once you've flagged the post, there is not much more to be done on your side. One possible exception is in cases when it might be unclear that the post is actually spam. (For example, if the post otherwise looks reasonable - perhaps because the content was copied from somewhere - but a punctuation mark or one word contains spam link.) In such cases, it might be useful to comment - in order to make spam more obvious to other users. If it doesn't look like spam just by glancing at it, you can use a custom moderator flag to explain to the moderators why it's spam.

Possibly - if you think that the spam might not be deleted quickly enough

  • You might leave a comment explaining to other users who see the same post what they should do. For example, you could link to this post in your comment.
  • Theoretically, you can even mention the post in chat to attract the attention of other users.
  • You are always welcome to report spam, or posts you think might be spam, in Charcoal HQ. Charcoal is a project with the specific goal to help with detecting spam in the Stack Exchange Network. Charcoal has a chat room, Charcoal HQ, in which a bot, SmokeDetector, reports all the spam it detects on all sites in the Stack Exchange Network.
    The people in Charcoal HQ have a lot of experience with combating spam and can give an opinion on posts that might be borderline, including checking to see if any domain, phone number, or email has been used in previously detected spam. Mentioning in Charcoal HQ spam posts which you find also helps the SmokeDetector bot detect similar spam in the future, as members of the project will update the things the bot looks for to detect spam, so the spam you report is detected in the future. If users in Charcoal HQ think the post is spam, they're sure to add some spam flags to help the post be deleted faster.
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    $\begingroup$ This answer was made CW with the intention that it is edited by the community - feel free to add further information to the answer if there is something worth adding. $\endgroup$ Commented Jun 12, 2019 at 17:04
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    $\begingroup$ "Editing the spam content out is counterproductive": you seem to be considering edits made so as to improve it. An edit can be used also: to vandalize/erase a potentially dangerous link (which I find useful – I'd just replaced the link with [erased link]), to remove a tag (which I find unnecessary), to partly hide an offensive statement if it includes names, or any action found to be useful before the spam is deleted. $\endgroup$
    – YCor
    Commented Jun 13, 2019 at 6:37
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    $\begingroup$ @YCor I cannot really respond to specific case you mention - since I did not see the post (and I do not see any today's post among SD reports either.) You made a valid point - important thing here is that even after the edit other users should be able to clearly recognize that it is a spam post. $\endgroup$ Commented Jun 13, 2019 at 9:34
  • $\begingroup$ What should one do with non-flaggable spam like mathoverflow.net/users/141968/yampolskyattorneys?tab=profile ? $\endgroup$ Commented Jun 16, 2019 at 2:09
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    $\begingroup$ @StevenLandsburg If I understand correctly, you mean spammy links in user profiles rather than in posts? This is (in my opinion) a separate issue and it was discussed on this meta before: Companies accounts allowed? and Flagging spam user. (Basically the same issue was mentioned also by Tim Campion in chat.) $\endgroup$ Commented Jun 16, 2019 at 4:43
  • $\begingroup$ @YCor One more disadvantage to editing is that if I see that the most recent activity was by a low rep user, I am very likely to check whether the post needs attention. (New users often need help with MathJax, tagging, etc. Post by low rep users are also more often off-topic or spam.) So if I see that the most recent activity on the question was by on an experienced user, it makes slightly less probable that I notice that the post was spam. (Reporting the post in charcoal in addition to editing it would resolve this problem.) $\endgroup$ Commented Jul 17, 2019 at 5:54
  • $\begingroup$ @MartinSleziak thanks, I ignored this aspect. I don't know what "reporting the post in charcoal" means. $\endgroup$
    – YCor
    Commented Jul 17, 2019 at 6:40
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    $\begingroup$ @YCor Reporting is covered in the last bulled point of this answer (current revision). I have left a few additional comments in chat. $\endgroup$ Commented Jul 17, 2019 at 7:16

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