Your traffic sources don't have to change; you could have been hit by ad clicking bots. I have had that line on and off over the years. If the amount of money gets to be significant, then yes, you probably want to start checking log files.

For a little more info on how Google is fighting ad fraud (and how big the problem is) read this post:

[webmasterworld.com...]

That happened to me as well....that's how I found this forum...I was investigating what that was....I too have been involved with Adsense for a while and I have never experienced that...I have been monitoring my sites like crazy....

Ok, I see - you know I didn't even look at my Payment screen this month (I almost never do) and I see that now the month-end clawback shows up as a line item in Payments, where it didn't before. As far as I can tell, this isn't a change in behavior, it's a change in reporting. Google used to use the line items for certain kinds of clawbacks during the month, but at the end of the month you'd just get an adjusted number with no explanation. Now we have the explanation. I am okay with this. In the post about the ad fraud, they did mention trying to be a little more transparent to the publishers, and maybe this is a piece of that.

I as well saw this "Invalid Traffic - AdSense for Content" today for the first time in Transaction history for last month. Too bad the transaction entry doesn't give the exact date so I could go back into my logs, however I do remember during the last week in May dealing with a bot from Russia named:

(Adsense Bot Banned) - To stop clicks write on email: invesem@yandex.com

Coming from a variety of East Euro compromised ISP and web servers. It hit a lot of pages before I discovered it and blocked, so I'm guessing this was the cause.

Anyone else have UAs of other click-fraud bots?

You'll find all kinds of bot information in this forum:

[webmasterworld.com...]

As for that one - did you put the "AdSense Bot Banned" in there? Yandex is a Russian search engine - if the spider actually came from them, it's not a click fraud thing.

@netmeg, thanks for the link but if you follow that link yourself and look through the posts you will find that I post in that forum several times a day. If the bots I was asking about were discussed there, I would certainly know it and would not have asked here, and yes I posted there about that particular Russian click-fraud bot about a month ago :)

[webmasterworld.com...]

I saw this article over on SearchEngineWatch.
[searchenginewatch.com...]
I wasn't exactly sure how/if it applies or benefits us Adsense publishers but it was interesting.

To confirm what Netmeg suspected, this is a reporting change visible in accounts from June onwards.

See "Increasing transparency of AdSense payments" on the AdSense blog.
[adsense.blogspot.co.uk...]

same here, got massive increase in May and double again in June

I've been seeing it in my Payments page since May, and the discounts are negligible.