If the received data is corrupted, it wasn't really "copied," was it?
Data packets sometimes become altered between the time they are transmitted and the time they are received. This occurs for a variety of reasons, and modern network protocols support "error checking and correction" (please search). Typically the numeric values of all the bytes of data in the packet are added up, and the result is then used to determine whether the packet was or was not received correctly (search "checksum"). Typically if the receiving node detects a "bad" packet (i.e. the received checksum doesn't match the sum of all the received bytes) a message is sent requesting another copy of the packet.