A sophisticated intruder can remain undetected while changing the users input before passing it on to the program. The first hint of tampering could be the discovery of a catastrophic problem. Sendmail Sendmail is a commonly used complex mail program that offers endless flexibility. Unfortunately, crackers exploit this flexibility to obtain unauthorized access to system data. Some of the bugs have only recently been fixed.
Many systems continue to use older versions sendmail.
Source code to tools that exploited weaknesses in the three-way handshake spread across the Cracker journals and the Internet. The SYN Flood attack sends a high volume of SYN packets to a target host and never responds with the rest of the handshake information, thus filling the targets data structures. This prevents legitimate processes from starting, paralyzing the target machine. Both known machines behind packet filtering routers and firewalls themselves are targeted disrupting individual and network service. The Ping o' Death takes advantage of Ips ability to fragment packets.