Q:

Is voting corrected triggered by another user or a periodic process of Stack Overflow?

Is the voting correcting of Stack Overflow triggered by a voting abuse, for example, another person who's constantly voting in a small period of time (a user targeting another user), or is a periodic process launched by the site itself?

A:

Rightly as you sourced, there is an automatic script that runs at 03:00 UTC.
Moderators may also flag the community team for a manual vote reversal where the script fails to reverse suspicious votes. Often this is brought to mod attention by vigilant community members who flag suspicious activity between users, we also have some tools that help us to detect suspicious votes. Plus we have our own experience to notice peculiar activity that may indicate voting fraud. Or by people contacting Stack Overflow directly.
One thing, most voting rings and voting fraud will be uncovered and it's taken seriously.

Continual abuse of the system which causes multiple reversals can lead to a suspension, but the review process for such a suspension is completely manual. No automated flags are ever generated for this behavior, though moderators do have access to some statistics that can help fight repeat offenders. If you find you are the victim of serial voting multiple times within a short time span, feel free to flag one of your own posts for moderator attention and explain the situation so they can investigate further.

This public view of your reputation reveals serial voting was reversed manually, as the reversal didn't coincide with the voting script being run overnight.

So for any users reading this, who attempt to bypass the voting fraud detection system, it's not a good idea, if you want to have an account in good order.
First time there's usually a warning, second time a suspension. If it's involves a complex voting ring, there's likely to be an immediate suspension.
Sock puppets usually invoke immediate suspension.
More reading:
How easy is it to "farm" reputation?
How many cheaters are caught per month; and what are the most common ways of cheating?

