The first four bytes of the map hold the filetype-identifier (usually "HM3W"). We'll leave that and the next 508 blocks alone. The next four (4th, 5th, 6th and 7th) bytes always hold hex: {0×00 00 00 00}. The following 508 bytes hold the map name, some data with unknown purpose, some more nullbytes and then finally, after byte 512 the MPQ file begins with "MPQ " and hex {0×20 00 00 00} Which is actually another (but smaller) header, and we can damage it:

Leave the string "MPQ " alone, and change hex {0×20 00 00 00} after it to hex {0×33 49 43 45} (We are at byte 516 now) and MPQ extractors will fail to open the map. Warcraft does not look at this information, so your map will be still playable. This method effectively crashes most deprotector scripts and programs, but any knowledgeable user can reverse the effect within seconds so it'll only help against beginners (People who don't know about this header corruption method).

Posted by 3ICE @ 12:41 am