Marcus Brutus as a Remote Interactive Authentication Agent

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Overview

What does Brutus do?

In simple terms, Brutus is an online or remote password cracker. More specifically it is a remote interactive authentication agent. Brutus is used to recover valid access tokens (usually a username and password) for a given target system. Examples of a supported target system might be an FTP server, a password protected web page, a router console a POP3 server etc. It is used primarily in two contexts :

To obtain the valid access tokens for a particular user on a particular target.

To obtain any valid access tokens on a particular target where only target penetration is required.

What is a target?

Well that depends on you. As far as Brutus is concerned a target is a remote system and possibly a remote user on a remote system, there is more. To engage any given target we require an attack method, generally we only perform one type of remote attack - that is we attempt to positivley authenticate with the target by using a number of access token combinations. A target may provide no available attack methods, it may provide one or it may provide several.

What is an attack method?

In the context of Brutus, it is a service provided by the target that allows a remote client to authenticate against the target using client supplied credentials. For instance a UNIX server sat on a network somewhere may be offering Telnet and FTP services to remote users. Both telnet and FTP require the remote user to authenticate themselves before access is granted. For both these services the required credentials are usually a username and a password, therefore we have two available attack methods : FTP or Telnet. Some target systems will provide no opportunity for attack (at least not a remote authentication attack), perhaps they offer no remote services, perhaps they only offer anonymnous remote services (that require no authentication) or perhaps they offer authenticated remote services but use mechanisms to prevent authentication attacks such as account lockout or one time passwords of some sort.

Which attack method is best?

Again, that depends on some factors which may include :

Is the target service available to any remote system? (Yes is good)

Does the target service require a single token (e.g. just a password) or multiple tokens (e.g. Username & password & domain?) (Single tends to be easier)

Does the target service feature account lockouts or large delays before returning the result of the authentication attempt?

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