FTP client/server and listen() implementation

Here is exploit. It works as described in NAI 1996 bulletin http://www.nai.com/nailabs/aspset/advisory/ftp-paper.asp but.... there are two points i'm disagree with NAI. 1. ftp console client under FreeBSD 2.2.x IS vulnerable 2. Inspite I don't treat FTP as secured protocol IMHO it's OS/software...