Snort related OSS tools

• snort - IDS
  
• snort inline (google search it - IPS)
  
• snortsam (IPS works with PF)
  
• snortalog (command line log generator)
  
• nessus (Linux and Windows, beat commercial ones)
  
• nikto - web server scanner
• acid/base (base is better)
  
• aanval (commercial one, but has one sensor free version)
  
• www.intertnetsecurityguru.com
  
• apache/php/pcre/mysql/adodb
• olinkmaster - autoupdate snort rules
• loghog (google search)
• swatch (google search)