Hi,
It is said that TCPIP is not secured, but how can I get into
a system without a login name and password ?
Thanks in advance for explanation.
Consty

It depends on the system architecture... TCP/IP is a protocol. It is noting but a rule of a road. It depends on the system creator wheather he/she will setup check posts in between the roads....

there is a lot of sysctl (kernel) options that will help securing tcpip:
syn_flood, backlog queue, tcp_syncookies (need kernel compiled with this option), tcp_synack_retries, tcp_rmem and tcp_wmem and so on.
sysctl options will also optimize speed of connection, concurrent connections allowed (server) and lots more.
Sysctl is used by linux and BSD, Solaris has different tools ("mdb" and "ndd"
commands).
Windows will require registry edition (and reboot).

Of course firewall is needed too.

It is said that TCPIP is not secured,
tcp/ip was really more desiged for reliably transmitting data than for use on hostile networks and as such doesn't have as many built-in security mechanisms as are probably necessary. Consequently thinks like sequence number guessing, tcp-based DoS attacks, MItM attacks, etc are all problematic. A complete re-write would be nice, but likely won't happen anytime soon.

but how can I get into a system without a login name and password
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