asp.net email text box validation

[frekster]

Hi.

Looking for some feedback on how to prevent a specific spam attack.

I have a form for a person to subscribe to a mailing list and they can
type in their email and click submit to subscribe. They then are sent
an email asking them to click a link to confirm. how can I prevent a
spammer from simply looping through thousands of emails and populating
my email list table with thousands of records and crashing the system?

I have to insert first to get the id of the inserted record to have the
person click the confirmation link in the email sent to them.

I.E

1. submit email address to system (validate it server side)
2. if all is ok, and it is good data, insert it into the db and get the
id of the record just inserted
3. construct the email to the person, construct a confirm link using
the id in the querystring, and send it out.
4. redirect to thank you page explaining confirmation email was sent.

So how can I stop a spammer from jamming thousands of emails in the
system in 10 seconds?

I thought of using some sort of time test, such as 3 seconds, and if a
submission happens in 3 seconds past the initial one, some how testing
for a loop and tons of hits, don't allow it. However, I am not clear on
how to program such a solution.

Does anyone have a way of programming this protection?

Any input is greatly appreciated.

Thanks.

Justin

 

[Guest]

Hello Justin,

I think the best technqiue of doing this is to use the concept of Image
Verification, which now everyone do, like if you signing for yahoo email, or
i am sure that you have experience, that while registering it ask you to
enter the verification code shown in a image that forms contain.

So in this manner as the spammer program cant read the word or numbers
written in the image, so the person have to read and then write it.. I think
this is the best way of hanlding the type of problem you have mentioned.

How to write that program,, which will generate a image on fly, i hope
following link will help you.

http://www.codeproject.com/aspnet/ImageVerification.asp

Best Luck,