Why would you want to block or strip attachments from Instant Messages?  Well, because these attachments do not get scanned by anti-virus because Instant Messages come over Port 80.  This opens a large risk to vulnerability to viruses, trojans and worms in your network if you are allowing users in the network to use Instant Messaging.  With Websense IM Attachment Manager, you can decide which file types you want to block and which you want to allow or you can block all attachments for IM.  If you want to learn more, visit Incaption here