It's been well known for some time that due to advancements in copier and printer technology, the quality of counterfeit magic cards has been improving.
If you think you have received a counterfeit card, please contact the trader who sent it to you immediately and let them know about your concerns. Please do so politely; even if the card turns out to be a counterfeit, this does not mean the trader who sent it to you knew that. On the other hand, you trade partner may state that they themselves cracked the card from a booster. Whether true or not, this is a valuable statement to collect for the resolution process.
If you are unable to come to a conclusion, on your own, please open a dispute for the card or cards you suspect as counterfeits. You may be asked to provide additional information, or to take the cards to an LGS for verification. Where this is not possible, you may have to ship the card to Cardsphere for examination.
Ultimately, if a card is judged to be a counterfeit, the responsibility is placed upon the sender, as per the Cardsphere Terms & Conditions.