Re: [Shutup] [ietf-smtp] Levels of proposals
Ned Freed <ned.freed@mrochek.com> Fri, 04 December 2015 15:35 UTC
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Date: Fri, 04 Dec 2015 07:17:55 -0800
From: Ned Freed <ned.freed@mrochek.com>
In-reply-to: "Your message dated Thu, 03 Dec 2015 20:53:32 -0800" <874mfy95mb.fsf@hope.eyrie.org>
References: <CABa8R6vfT-9=51B32++eUAVeq5xuhTNUuv62yeO+W6AErRFnDQ@mail.gmail.com> <5660F3A1.7060807@mustelids.ca> <1449195108085-9ef6f394-96f931b3-20b99bd2@fugue.com> <87k2ov7xly.fsf@hope.eyrie.org> <1449196775597-73137a19-d32873ba-cad85c2a@fugue.com> <87a8pq98m3.fsf@hope.eyrie.org> <1449202966785-573af732-876dd2d9-16d51672@fugue.com> <874mfy95mb.fsf@hope.eyrie.org>
To: Russ Allbery <eagle@eyrie.org>
Archived-At: <http://mailarchive.ietf.org/arch/msg/shutup/HxlSNUdytvp6BIaYXDz53uFHl30>
Cc: shutup@ietf.org, Ted Lemon <mellon@fugue.com>, ietf-smtp@ietf.org
Subject: Re: [Shutup] [ietf-smtp] Levels of proposals
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> Oh, you didn't mean throttle by id/password pair. You meant throttle > purely by user ID. An important reason not to have a pure user ID block is it provides an easy way to block someone's access to their email: Simply set up a system to constantly bang on their account with the wrong password, and they're effectively locked out. An alternative is a pure user ID slowdown (as opposed to a complete block), but there are limits to how effective this can be. Bad guys can afford to be patient whereas legitimate clients time out pretty quickly, turning a slowdown back into a block. > There are two reasons (well, at least -- maybe more) why this doesn't help > as much as it sounds like it would, particularly in the case of SMTP AUTH. > One is that the attacker just changes the pattern of their brute force > search to distribute it across more known accounts or across more time, so > they just probe more accounts with fewer passwords. It's all the same to > them; they're just doing a combinatoric search, and varying parameters > that way doesn't have too negative of an impact on their ability to > compromise accounts. > Another reason is more specific to SMTP AUTH: dozens of incorrect login > attempts for the same username is a common *legitimate* pattern for users > who have a single misconfigured device (a typo in their password, for > instance. (And thanks to cell phones, those failed logins often come from > a huge variety of IP addresses.) SMTP UAs often retry authentication > pretty aggressively and will happily look like an attacker. If you lock > an account for that pattern, you can lock out that user's other legitimate > devices. Web sites usually don't have to worry as much about automated > incorrect legitimate login attempts. I note that this also applies to IMAP and POP3. In fact the most common case is probably going to be legitimate IMAP clients banging on the door. Sometimes a single client even does it from multiple threads. Ned
- [Shutup] Levels of proposals Brandon Long
- Re: [Shutup] Levels of proposals Stephen Farrell
- Re: [Shutup] Levels of proposals Chris Lewis
- Re: [Shutup] [ietf-smtp] Levels of proposals Ted Lemon
- Re: [Shutup] [ietf-smtp] Levels of proposals Ted Lemon
- Re: [Shutup] [ietf-smtp] Levels of proposals Ted Lemon
- Re: [Shutup] [ietf-smtp] Levels of proposals Russ Allbery
- Re: [Shutup] [ietf-smtp] Levels of proposals Russ Allbery
- Re: [Shutup] [ietf-smtp] Levels of proposals Russ Allbery
- Re: [Shutup] [ietf-smtp] Levels of proposals Chris Lewis
- Re: [Shutup] [ietf-smtp] Levels of proposals Chris Lewis
- Re: [Shutup] [ietf-smtp] Levels of proposals Chris Lewis
- Re: [Shutup] [ietf-smtp] Levels of proposals Ned Freed
- Re: [Shutup] [ietf-smtp] Levels of proposals Hector Santos
- Re: [Shutup] [ietf-smtp] Levels of proposals Chris Lewis
- Re: [Shutup] [ietf-smtp] Levels of proposals John Levine
- Re: [Shutup] [ietf-smtp] Levels of proposals Ned Freed
- Re: [Shutup] [ietf-smtp] Levels of proposals Chris Lewis
- Re: [Shutup] [ietf-smtp] Levels of proposals Brandon Long