Akismet is not needed. With all the downloads so far I have yet to hear a voice that claims to have received unsolicited spam. Certainly, there is zero you can do against a human typing in nonsense, but Akismet wouldn’t catch those either.
Here is a more detailed answer from the cforms forum:
Here is what you can do to tighten security:
1. Add a Question & Answer field
2. Add a CAPTCHA image (with v7.2 you can design it)
3. Add regular expressions for key fields
1. e.g. a name field can only contain [A-Za-z .\-]*
2. a phone number only numbers [0-9 \-\+]*
3. etc.
4. Create a "honey pot"
1. Add an single line input field with a regexp that only validates if the field is left empty!
2. Via CSS set the above field to not show!
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Please also visit the cforms forum »