Following methods to prevent from Cheating:
(1)   Add Advertiser Security Token:  To read more, refer to question - “how to use advertiser security token”
(2)   Add global IP Whitelist of Postback Server or aimed at a single advertiser add whitelist. To read more, refer to question - “how to use whitelist”
(3)   You can open Filter Bot Traffic at Settings -  Tracking Settings
(4)   By adding offer events: Set the relationship and end point to these events. So, when anything goes wrong before the end point’s event occur and if the conversion is not recorded, you can download the conversion report and know which offer is according to the normal sequence. The offer which is not in accordance with the normal sequence of conversions can be considered as cheating.