Most password-cracking scenarios focus on attacks that convert a captured hash to its plain-text password equivalent using an offline attack and hash or rainbow table database. Capturing password hashes assumes a lot. In most cases, the attacker must have highly privileged access (admin or root) to get to the hashes; if they do, they can inflict much more other damage. So why just discuss password cracking?
Further, in the Windows world, a remote attacker must have local administrator access on a computer and NetBIOS access, which is often blocked by the perimeter firewall. Despite popular belief, today's Windows logon password hashes cannot be sniffed off the wire. Plus, if an attacker can get the hash, he or she can conduct a "pass-the-hash" attack and not worry about converting it in the first place.
[ Roger shares more advice on managing passwords in these Security Adviser posts: "Password size does matter" | "Getting a grip on better password hashes" | "Ask better password questions" ]
Don't be lulled into a false sense of security, though: A complex, six- to eight-character password may have been sufficient 10 years ago, but it's certainly not today. Most of the Linux/Unix systems I've reviewed do not enable their account lockout policy. In the Windows world, the true administrator account cannot be locked out, and some software programs don't log against the account lockout policy. Many companies are disabling the account lockout policy to prevent automated worms, such as Conficker, from locking out all the user accounts and causing an indirect DoS event.
Moreover, most companies still lack a sufficiently adequate auditing system to alert admins of repeated failed logon attempts -- even if the number exceeds the hundreds of thousands. So a remote attacker can enumerate all of your external access points (Outlook for Web Access, Terminal Server, SharePoint, FTP, SSH, RDP, Telnet, and so on) and guess away against your administrator account until he or she breaks it.
