There is a plugin in wordpress blog which track clicks on the ads and their ip addresses , If some IP address is seen to be making fraudulent clicks then he will report that to you and you can report that to google adsense in advance. thats all what i know about this.
I think Google can automatically detect these smaller amounts of invalid activity and just remove it. Try WP Plugin - http://wordpress.org/plugins/ozh-who-sees-ads/ This may help you little bit -https://support.google.com/adsense/answer/16737?ctx=as2&rd=1