I will start with two real-life scenarios.
Recently another user complained about a down-vote on their post. (Well, we have lot of such posts here on meta.) But they also mentioned in a comment, that other answers were downvoted by the same user. We cannot know for sure whether they were downvoted by the same uses, but I checked profiles of the other answerers and I saw negative reputation changes in all of them but one with almost the same timestamp. Three answers are probably too few to be caught by software, but we can imagine somebody doing similar thing on a question with 10 answers.
To have also example with upvotes: I procrastinated on this site today longer than usual. As a consequence I run out of votes. I saw several nice post after that, so I copied the links with the plan to come here the next day and upvote them. So I will probably cast several votes in quick succession. I have already read the posts. Now I will only copy the link and upvote for each of these posts. I wonder whether it is possible that my votes will be detected as serial upvoting and reversed. (Or if I might be even suspended for voting irregularities.)
I saw here that serial voting is defined in the following way: "Serial voting is the act of casting many upvotes or downvotes on the posts of a specific user without proper reason. Also known as voting fraud." Judging by that definition, if the votes are not directed to the same users, that should not be considered serial voting. But I still wanted to check whether SE software checks also for upvotes/downvotes directed not only to a single user. (To know whether I am doing something wrong. And also to know whether some suspicious vote patterns can be caught and reversed.)
TL;DR: Is casting votes in the quick succession (but not on the post of the same user) detected by SE software? Are such votes reversed in some cases? Can a user be suspended for such votes?