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There is a large IMAP4 exploit and this documents the fix

gkeen/notes-2pair- telnet rachel 143
Trying 172.16.60.148...
Connected to rachel.
Escape character is '^]'.
* OK rachel.physio-control.com IMAP4rev1 v10.223 server ready
ls
ls BAD Missing command
which 
which BAD Missing command
root
root BAD Missing command
0 logout
* BYE rachel.physio-control.com IMAP4rev1 server terminating connection
0 OK LOGOUT completed
Connection closed by foreign host.

<<<<<<<<This means someone can get in through port 143>>>>>>>>>>>>>>>>>>
vi /etc/inetd.conf
comment out imap reference

vi /etc/services
and comment out imap reference

kill -HUP (pid of inetd)  this sends a hangup and reread config file