Enter the spim doctor

IBM has a simple solution to the burgeoning curse of “spim” – spam delivered via instant messaging. In US patent application 2004/0143632, it describes software that automatically responds to every incoming instant message by asking the sender’s computer for a code that the receiver has previously distributed to family, friends and anyone else they are happy to be contacted by. If the sender’s computer replies with the required code, the instant message is delivered with no perceptible delay. Otherwise, it is deleted, along with any further messages from the same source.