FreeBSD Security Advisory – When the arc4random random number generator is initialized, there may be inadequate entropy to meet the needs of kernel systems which rely on arc4random; and it may take up to 5 minutes before arc4random is reseeded with secure entropy from the Yarrow random number generator.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/72257/FreeBSD-SA-08.11.arc4random.txt
Source: https://packetstormsecurity.com/files/72257/FreeBSD-SA-08.11.arc4random.txt.html