The worm spreads by exploiting a buffer overflow discovered by the Polish security research group Last Stage of Delirium in the DCOM RPC service on the affected operating systems, for which a patch had been released one month earlier in MS03-026 and later in MS03-039. This allowed the worm to spread without users opening attachments simply by spamming itself to large numbers of random IP addresses. Four versions have been detected in the wild. These are the most well-known exploits of the original flaw in RPC, but there were in fact another 12 different vulnerabilities that did not see as much media attention.