How to block Webform spam based on keyword strings? Short Version: I would like to block Webform submissions that contain strings e.g. mail.ru in the webform textarea field. 

Recently I am seeing a lot of fake webform submissions. I am already using honeypot contrib module and I have added quite a number of IP addresses to the server firewall. However there is still some spam coming through. For now I don't want use Captcha. Luckily those spammers always using recurring pattern e.g. same domain name.

How I can automatically block submission that contain certain strings? Using the rules + webform_rules module and Regex doesn't allow me to choose the Webform email field as data selector. selected-webform:0 doesn't look valid. What's the right way to block webform spam?

{ "rules_blocking_fake_registration" : {
"LABEL" : "Blocking fake registration",
"PLUGIN" : "reaction rule",
"OWNER" : "rules",
"REQUIRES" : [ "rules", "webform_rules" ],
"ON" : { "webform_rules_submit" : [] },
"IF" : [
  { "node_is_of_type" : {
      "node" : [ "node" ],
      "type" : { "value" : { "contactform" : "contactform" } }
    }
  },
  { "text_matches" : {
      "text" : [ "selected-webform:0" ],
      "match" : "plusgmail.ru",
      "operation" : "regex"
    }
  }
],
"DO" : [
  { "block_ip" : [] },
  { "mail" : {
      "to" : "admin@address.com",
      "subject" : "[site:name]: Blocking user [data:e_mail-value]",
      "message" : "E-Mail Adresse: [data:e_mail-value]",
      "language" : [ "site:current-user:language" ]
    }
   }
  ]
 }
}


I really appreciate any comments and help.
Try Webform Validation module. It adds validation options for webforms. One of these extra options is "words blacklist", where you can specify the list of strings that should not appear in your field. The spammers will get validation error and will not be able to submit the form.