Whew! Check your logs, see if there's activity that is unusual... take steps as necessary!

g remains the only "real" game in town so you will want to make the effort... besides, two sources of income are better than one...

As said check your logs. That said:

The most common reason for consistent level claw backs is perceived inadvertent clicks; to which a webdev often has available solutions.

The most common reason for sudden mass or spike claw backs is being an inadvertent ‘beard’ site for a click fraud operation. To hide the intended recipient of click fraud revenue the bots also click ads on a great number of other sites. However, once such an operation is noticed all associated clicks are rolled back, both the actual fraud target plus the large collateral damage.

The only preemptive solution available to a webdev is bot mitigation, often not practicable for hosted sites directly; an often overlooked value when deciding on a host is their bot blocking capability.

It is a shock and severe pita whenever such a mass clawback happens, exacerbated by the causal silence of the ad network. From the glass half full perspective such an event should be a one off.

If not then you really need to consider how best to block the bots as you (or your host) is on a list of easy targets.

Best wishes.

I had my biggest clawback ever (5%) in December. In that case, it was easy to see why: One "visitor" clicked an ad 10 times, and for whatever reason Adsense's real-time filter didn't catch it. Luckily, that did seem to be a one-off, and January was more or less normal.

That info probably doesn't help any, but I wanted to chime in because my Analytics has been showing a larger number of clicks not counted since mid-October (though it's gone down substantially as time has passed). Dumb bots, I guess.

I have another question. If Google knows there is click fraud, they must know the IP that the clicks came from. Why don't they share this information?

Click fraud can come from distributed sources, so there may not be one IP address involved but many. A common IP address is also just one of the fingerprint techniques Google can use to identify invalid clicks.

Go to Google Analytics > Audience > Technology > Network > select Adsense and sort the report by clicks (make sure date range is Jan 20). If a network has very high ctr, select the network, and select browser version as secondary dimension. Using the UA and network you can weed out if there was a click attack.

@levo - Thank you very much!

@levo I cannot select AdSense because I can't find it on that network page. Can you give me a clue? Thanks.

The link to select Adsense is just above the graph on that page.

I think you need to have your Google Analytics and AdSense accounts linked before you can Select the AdSense information in Analytics.

Thanks levo and lammert. I thought I had my AdSense account linked to Analytics, but I'll check that.

Yes, my accounts are linked, but what I need is nowhere to be found.

[imgur.com...]

levo, thank you very much. I simply do not have anything like that on my panel. :(

Double check if they're linked.

[support.google.com...]

I double-checked. They are indeed linked. thank you.