* Unix
* Windows
* QNX
* Web server Apache,Nginx,IIS.
* Terminals: Citrix.
* Databases: MySQL,MSSql,Oracle.
* Proxy servers: Squid, 3proxy.
* FTP servers: Proftpd, ftpd, pure-ftpd.
* DNS: bind or named.
* Firewall configuration, NAT, Masquerade: iptables, ipfw.
* Mail SMTP: Exchange,Sendmail, Postfix+sasl, Qmail,Exim.
* POP3/IMAP: Exchange,qpopper, pop3d, courier.
* Security: Snort, ettercap, Nessus, nmap, arpwatch, Ethereal, dsniff, tcpdump, chkrootkit, rkhunter.