[Andrew] recently got scammed on an SD card purchase and put together a small tool that can help you determine if you’ve had the wool pulled over your eyes as well.
You see, he purchased a set of MicroSD cards, all of which had an advertised capacity of 4GiB. When he tried to use them, they all failed to write more than about 115MiB of data, so he knew something was up. He sat down with some tools that can be used to check the actual capacity of flash media, but he says they were unbelievably slow to scan the cards.
While he waited for one of the scans to complete, he decided to create a utility of his own that would do the same thing in a fraction of the time. His quick and dirty application, called “Scam-o-Matic”, writes random data to the card, double-checking the written region to ensure that data can be read back. If it finds errors your card is likely either a fake or damaged, but if not, it automatically prepares the media for use.
Obviously this sort of situation is relatively rare, but if you think that you have picked up some shady SD cards, be sure to check out [Andrew’s] Github repository.