There some people who serial upvote with a fake account in order to gain reputation. But I am wondering if some people spread out their votes and vote on some other questions and answers like they are doing it legit in order to cheat. More importantly, is it possible to cheat this way?

For example, maybe a user uses a fake account and upvotes only $2$ or even $1$ of his posts per day, and spends a good amount of votes on other questions / answers. Does the serial upvoting script detect this? If not, how could a moderator detect this kind of behaviour?

• there won't be much damage at 2 upvotes per day.
– Guy
Mar 21, 2014 at 4:26
• This is second (third?) hand information, but they say that they know if somebody has a fake account (aka sock puppet). That's mostly ok, but kept under surveillance, and the `true' account and the sock puppet must not cross paths. One voting the other would raise a flag. Mar 21, 2014 at 5:58

Stack Exchange scripts detect both short-term and long-term unusual voting patterns. For an example of the latter system in action, see this thread:

the votes which were removed did not all come from the same day. You and three coworkers have been coordinating votes between yourselves for a couple of months now, and almost all of those votes were invalidated at once.

Besides invalidating the fraudulent votes, the scripts alert the moderators: there is a panel "Suspicious voting patterns" among the moderator tools.

Also, a moderator whose attention was raised for whatever reason can get the list of users who upvoted a given user the most, and vice versa.

Though the mills of [Supreme Moderator] grind slowly; Yet they grind exceeding small

• I'll just add that while the ♦-mods can view information about voting patterns, we cannot alter (i.e., invalidate) votes. If not done by the automatic script, this is accomplished by SE employees (usually community managers such as Grace Note and Shog9, among others). While we from time to time point out behaviour that we find suspicious, the SE community managers do not always agree with our findings. Mar 21, 2014 at 6:21

For larger scale strategic upvoting, see above. However, those keen (petty?) enough about raising their scores are also aware of thresholds that actually trigger attention and action. I have chat transcripts of high rep users discussing how many per day will - in practice - stay undetected if used to mutually upvote between accounts of a user and a friend, concluding that this is the amount they take advantage of each day.

I would just ignore it. Maintaining a system, and a system's integrity, for a non-commercial site of this volume is hard. If someone really is hell-bent to abuse it, they might succeed; but just pity them and do your own thing.