Add some useful rules to yara

[radare]

It would be nice to be able to have rules for:

• hostnames
• ipv4 and ipv6
• credit-card numbers
• emails

for credit cards we should cook some regexes compatible with libmagic from this: http://www.paypalobjects.com/en_US/vhelp/paypalmanager_help/credit_card_numbers.htm

Moved from https://github.com/radare/radare2/issues/1139

[Vlurk]

In regards to credit card... There should also be a small validation that the number is indeed, "valid" according to the mathematical formula described here: http://www.freeformatter.com/credit-card-number-generator-validator.html

Else, the rule is going to fire so often (in corporate environments at least) that nobody will seriously consider using it. The false positive rate will be too high.

[sylvainpelissier]

r2yara has its own repository now.