A Look Back at "Security Problems in the TCP/IP Protocol Suite"
Source: AT&T Labs-Research
Several points are immediately obvious from this analysis. The first, surely, is that in general, relying on the IP source address for authentication is extremely dangerous. Fortunately, the Internet community is starting to accept this on more than an intellectual level. The Berkeley manuals have always stated that the authentication protocol was very weak, but it is only recently that serious attempts have been made to correct the problem. Kerberos and SunOS 4.0 have their weaknesses, but both are far better than their predecessor. More recently, an extension to the Network Time Protocol (NTP) has been proposed that includes a cryptographic checksum.