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Browse - Computer Tips - Can I make my Internet-facing daemons more secure?

Date: 2007nov7
Updated: 2009dec7
Keywords: Security Through Obscurity

Q.  Can I make my Internet-facing daemons more secure?

A.  Its a good idea not to give potential hackers the name
and version of your server.  They might know a crack for it.
Many Linux servers do just this by default.
You can change the following configuration files to display
a generic greeting:

Dovecot
-------
File /etc/dovecot.conf
login_greeting = IMAP/POP Server ready
vsftpd ------ File /etc/vsftpd/vsftpd.conf
ftpd_banner=FTP Server ready
Proftpd ------- File /etc/proftpd.conf
ServerIdent on "FTP Server ready"
Postfix ------- File /etc/postfix/main.cf
#smtpd_banner = $myhostname ESMTP $mail_name #smtpd_banner = $myhostname ESMTP $mail_name ($mail_version) mail_name = The-Mailer
Apache ------ File /etc/httpd/conf/httpd.conf
ServerTokens Prod ServerSignature Off
Test ---- Restart the services and check with these commands:
telnet localhost pop3 </dev/null sleep 1 | telnet localhost ftp telnet localhost smtp </dev/null
Test Apache my hitting an page that doesn't exist: http://www.example.com/page_that_does_not_exist PHP --- If you run PHP scripts then you have many public URLs ending in .php which tells everyone that they are written in PHP. But they don't have to end in that extension. In file /etc/httpd/conf.d/php.conf change:
AddHandler php5-script .php AddType text/html .php
to
AddHandler php5-script .hello AddType text/html .hello
Then rename your scripts. Of course, you can use any extension that isn't already in use -- such as your company name. Port knocking ------------- Using knockd you can make a port appear to be closed until a friendly user accesses a sequence of other ports. Crazy obscure.

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