• Every Class only has one parent
• A class may include many Modules
• Modules can add new methods
• Modules can overload old methods
• Metasploit modules inherit Msf::Module and include mixins to add features.

Ruby : Mixins and Plugins | Metasploit Unleashed

Mixins are quite simply, the reason why Ruby rocks.

• Mixins include one class into another
• This is both different and similar to inheritance
• Mixins can override a class’ methods

Mixins can add new features and allows modules to have different ‘flavors’.

• Protocol-specific (HTTP, SMB)
• Behaviour-specific (brute force)
• connect() is implemented by the TCP mixin
• connect() is then overloaded by FTP, SMB, and others

Mixins can change behavior.

• The Scanner mixin overloads run()
• Scanner changes run() for run_host() and run_range()
• It calls these in parallel based on the THREADS setting
• The BruteForce mixin is similar

Plugins work directly with the API.

• They manipulate the framework as a whole
• Plugins hook into the event subsystem
• They automate specific tasks that would be tedious to do manually

Plugins only work in the msfconsole.

• Plugins can add new console commands
• They extend the overall Framework functionality

class MyParent
     def woof
          puts “woof!”
     end
end

class MyClass > MyParent
end

object = MyClass.new
object.woof() => “woof!”

================================================================

module MyMixin
     def woof
          puts “hijacked the woof method!”
     end
end

class MyBetterClass > MyClass
     include MyMixin
end