Irule to block Requests with specific word

Try this code to prevent issue. the problem may be the variable payload contains space and the code fails as the following string in the payload is read as a new argument. this solution will bypass the issue but may let some SPAM get in.

 Collect a request payload
when HTTP_REQUEST {

  if {[HTTP::method] eq "POST"}{
     Trigger collection for up to 1MB of data
    if {[HTTP::header "Content-Length"] ne "" && [HTTP::header "Content-Length"] <= 1048576}{
      set content_length [HTTP::header "Content-Length"]
    } else {
        set content_length 1048576
    }
     Check if $content_length is not set to 0
    if { $content_length > 0} {
      HTTP::collect $content_length
    }
  }
}

when HTTP_REQUEST_DATA {
    set payload [HTTP::payload]
    catch {
        if {[class match $payload contains "restricted_dg"]} {
            log local0. "Rejecting restricted content" 
            reject
        }
    }
    HTTP::release
}