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

Date: 2007nov7 Updated: 2024mar12 Keywords: Security Through Obscurity, hide, Prod, signature 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 exploit 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/
#smtpd_banner = $myhostname ESMTP $mail_name #smtpd_banner = $myhostname ESMTP $mail_name ($mail_version) mail_name = The-Mailer
Jetty ----- In file $JETTYHOME/etc/jetty.xml Set this to false at the bottom:
<Set name="sendServerVersion">false</Set>
Apache ------ File /etc/httpd/conf/httpd.conf
ServerTokens ProductOnly ServerSignature Off
Nginx ----- File /etc/nginx/nginx.conf
http { ... server_tokens 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 by visiting a page that doesn't 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
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.