Re: Why do you have to worry about Brute Force Attacks?

On the other hand...

Be aware that attackers can use the lockout feature to cause a denial of service attack. If I don't like you, I can just set up a script that fails to log in as you over and over again, and you'll just be locked out all the time.

Having the lockout only last 15 minutes is good, but still vulnerable. One of the systems where I work actually disables your account after X failed logins and we have to call an admin to get re-activated. Very very bad...

You have to decide which is worse the vulnerability of letting someone try 20,000 logins or the vulnerability of making it easy to lock your users out.

Comment on Re: Why do you have to worry about Brute Force Attacks?

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Re^2: Why do you have to worry about Brute Force Attacks? by DrHyde (Prior) on Sep 27, 2006 at 09:38 UTC
Be aware that attackers can use the lockout feature to cause a denial of service attack. This is why I think it's better to make the system slow down instead of just barring access. After one unsuccessful login, make them wait a second before trying again. After two, make them wait three seconds. After another, nine seconds, and so on. This prevents brute-force attacks by making them time-prohibitive while not noticeably slowing down a legitimate user who can't remember which of his three passwords he used for your service. Take a look at Tie::Scalar::Decay for an easy way of implementing it. I suggest putting Tie::Scalar::Decay values into a hash which is keyed by the IP address from which the login attempts are coming, and the username they're trying to authenticate as.	[reply]
Re^2: Why do you have to worry about Brute Force Attacks? by Argel (Prior) on Sep 27, 2006 at 00:36 UTC
That is a good point. Does anyone know how some of the big websites like say Amazon or Yahoo deal with this? I'm inclined to say that if there are privacy concerns that it would be better to beef up security and try to figure out ways to deal with the DDOS attacks.	[reply]
Re^2: Why do you have to worry about Brute Force Attacks? by Anonymous Monk on Sep 27, 2006 at 09:01 UTC
the solution to this is for both the id and password to be secret	[reply]