Abstract


  • Configuration files in Linux that act as gatekeepers with rules that control where data can flow
  • Contains pattern-matching rules (regex, IP range and keywords) and actions (ACCEPT, DROP, LOG)

4 Types

Network filters:

Log filters:

Access filters:

  • Control user/service permissions
  • Example: hosts.allow/deny, sudoers

Content filters:

  • Process data streams or files
  • Example: web server rules, email filters