Hi list,
We frequently warn clients of the risks of brute force or automated
attacks against their sites and recommend the use of CAPTCHA
(www.captcha.net) systems, or "secret questions" to mitigate this risk.
For example:
- The registration process does not use captcha like systems and could
allow attackers to use an automated script to generate thousands of
fictitious users. These users can then be used to perform transactions
that could lead to financial loss (e.g. costs due to rejected credit
card), or waste resources through database access (and wasted storage).
- The password reminder mechanism requires only the user's email
address which is used to send them an email for resetting their
password. But since it requires no further auth from the user (such as
an answer to a secret question), an attacker could enumerate all the
valid email addresses registered to the site by writing a brute force
script and using a database of email addresses (this may be
particularly useful to a competitor). Of course, if the email address
is used as the username, this problem becomes more serious.
Although these risks are real - and I don't doubt they will be used in
the future - I'm not aware of any attacks of this sort being conducted
in the past. Is anyone aware of these types of attacks in real-world
scenarios? Do you think these pose a serious threat?
regards,
Stephen
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